CHARACTER RETRIEVAL METHOD AND APPARATUS, ELECTRONIC DEVICE AND MEDIUM TECHNICAL FIELD The present application relates to the field of artificial intelligence, and in particular to a character retrieval method and apparatus, an electronic device and a medium. BACKGROUND Artificial intelligence is a branch of computer science and is considered as one of the three main cutting-edge technologies in the 21st century. In the past three decades, artificial intelligence has developed rapidly, and has been widely used in many fields, and achieved fruitful results. The information retrieval technology in artificial intelligence can be used to retrieve Chinese characters, etc. Existing Chinese character retrieval methods mainly include radical- based retrieval, pinyin alphabetic order-based retrieval, etc., which are all designed mainly in view of habits of Chinese native speaker users, so it is difficult to retrieve Chinese characters without mastering the basic knowledge of Chinese such as radicals and pinyin. SUMMARY The present application aims to provide a character retrieval method and apparatus, an electronic device and a medium, which can reduce the difficulty of Chinese character retrieval to a certain extent. According to one aspect of embodiments of the present application, there is provided a character retrieval method, which includes: acquiring a target stroke, retrieving candidate components containing the target stroke, and displaying the candidate components; in response to a component selection instruction to select a target component from the candidate components, displaying the target component, and displaying at least one position selection button for selecting a position of the target component; in response to a position selection instruction to select the position of the target component received through the at least one position selection button, acquiring a target position corresponding to the position selection instruction, retrieving candidate characters with the target component at the target position, and displaying the candidate characters; and in response to a character selection instruction to select from the candidate characters a character to be retrieved, retrieving the character to be retrieved. According to one aspect of embodiments of the present application, there is provided a character retrieval apparatus, which includes: an acquisition module configured to acquire a target stroke, retrieve candidate components containing the target stroke, and display the candidate components; a component selection module configured to, in response to a component selection instruction to select a target component from the candidate components, display the target component, and display at least one position selection button for selecting a position of the target component; a position selection module configured to, in response to a position selection instruction to select the position of the target component received through the at least one position selection button, acquire a target position corresponding to the position selection instruction, retrieve candidate characters with the target component at the target position, and display the candidate characters; and a character retrieval module configured to, in response to a character selection instruction to select from the candidate characters a character to be retrieved, retrieve the character to be retrieved. In one embodiment of the present application, based on the foregoing scheme, the acquisition module is configured to: in response to a retrieval instruction, acquire basic strokes and display the basic strokes; and in response to a stroke selection instruction to select the target stroke from the basic strokes, acquire the target stroke, retrieve the candidate components containing the target stroke, and display the candidate components. In one embodiment of the present application, based on the foregoing scheme, before acquiring the basic strokes, the acquisition module is further configured to: acquire a character image of the character to be retrieved; segment the character image to obtain a plurality of image segments; acquire a stroke in each image segment at a given position; and determine the basic strokes based on the strokes at the given positions. In one embodiment of the present application, based on the foregoing scheme, the acquisition module is configured to: display the basic strokes in a stroke display page; and in response to the stroke selection instruction received through the stroke display page, retrieve the candidate components; and switch from the stroke selection page to a component selection page, and display the candidate components in the component selection page. In one embodiment of the present application, based on the foregoing scheme, the component selection module is configured to: in response to the component selection instruction received through the component selection page, switch from the component selection page to a character selection page, and display the target component and the at least one position selection button in the character selection page; and acquire a preset position, retrieve preset characters with the target component at the preset position, and display the preset characters in the character selection page; and the position selection module is configured to: replace the preset characters with the candidate characters in the character selection page. In one embodiment of the present application, based on the foregoing scheme, a plurality of the position selection buttons are provided, and after obtaining the preset position, the component selection module is further configured to: mark in the character selection page one or more position selection buttons corresponding to the preset position; and after acquiring the position selection instruction, in the character selection page, unmark the one or more position selection buttons corresponding to the preset position, and mark one or more position selection buttons corresponding to the position selection instruction. In one embodiment of the present application, based on the foregoing scheme, the position selection module is configured to: acquire one or more position selection buttons selected in the character selection page according to the position selection instruction as the one or more position selection buttons corresponding to the position selection instruction; and acquire a position of the one or more position selection buttons corresponding to the position selection instruction in the plurality of position selection buttons as the target position. In one embodiment of the present application, based on the foregoing scheme, the number of the position selection buttons is at least nine, and the position selection buttons are arranged into a square array. In one embodiment of the present application, based on the foregoing scheme, the acquisition module is configured to: retrieve candidate components with the target stroke as a starting stroke. In one embodiment of the present application, based on the foregoing scheme, before responding to the component selection instruction, the component selection module is further configured to: if a stroke adding instruction is received, retrieve next candidate strokes in the same component as the target stroke, and display the next candidate strokes; in response to a next stroke selection instruction to select a next target stroke from the next candidate strokes, acquire the next target stroke, and retrieve candidate components containing the target stroke and the next target stroke; and display the target stroke and the next target stroke, and display the candidate components containing the target stroke and the next target stroke. In one embodiment of the present application, based on the foregoing scheme, before responding to the next stroke selection instruction, the component selection module is further configured to: in response to the stroke adding instruction received through a stroke adding button, move the target stroke away from a reserved position for displaying the next target stroke in a stroke display area; and in response to the next stroke selection instruction, display the target stroke in the stroke display area, and display the next target stroke in the reserved position in the stroke display area. In one embodiment of the present application, based on the foregoing scheme, before responding to the character selection instruction, the character retrieval module is further configured to: if a component adding instruction is received, acquire a target stroke of a next component, retrieve next candidate components containing the target stroke of the next component, and display the next candidate components; in response to a component selection instruction to select a next target component from the next candidate components, display the next target component, and display at least one position selection button for selecting a position of the next target component; and in response to a position selection instruction to select the position of the next target component received through the at least one position selection button, acquire a next target position corresponding to the position selection instruction, retrieve candidate characters with the target component at the target position and the next target component at the next target position, and display the candidate characters. According to one aspect of embodiments of the present application, there is provided a computer-readable program medium, which stores computer program instructions that, when executed by a computer, cause the computer to perform any of the methods described above. According to one aspect of embodiments of the present application, there is provided an electronic device, which includes: a processor; and a memory storing computer-readable instructions which, when executed by the processor, enable implementation of the method as described in any one of the above embodiments. According to one aspect of embodiments of the present application, there is provided a computer program product or computer program including computer instructions stored in a computer-readable storage medium. The processor of the computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions to cause the computer device to carry out the methods provided in the various alternative embodiments described above. The technical scheme provided by the embodiments of the present application may have the following beneficial effects: in the technical schemes provided by some embodiments of the present application, by acquiring the target stroke, retrieving the candidate components containing the target stroke, and displaying the candidate components, a user is prompted to select the target component from the candidate components; by displaying the target component in response to the component selection instruction to select the target component from the candidate components, and displaying at least one position selection button for selecting the position of the target component, the user is prompted to select the position of the target component; by acquiring the target position corresponding to the position selection instruction in response to the position selection instruction to select the position of the target component received through the at least one position selection button, and retrieving the candidate characters with the target component at the target position, the number of the candidate characters can be greatly reduced, and then the candidate characters are displayed, so that the user is prompted to select from the candidate characters the character to be retrieved; and the character to be retrieved is retrieved in response to the character selection instruction to select from the candidate characters the character to be retrieved. By displaying the candidate components, the position selection buttons and the candidate characters, the user can be prompted to give a selection instruction, thus reducing the difficulty of retrieving the character to be retrieved. In addition, the candidate characters are determined by the combination of the target component and the target position, and the position of the target component in the character to be retrieved is not limited, as long as the target component corresponds to the target position, which further reduces the difficulty of retrieving the character to be retrieved. It is to be understood that the foregoing general description and the following detailed description are exemplary only and do not limit the present application. BRIEF DESCRIPTION OF DRAWINGS The accompanying drawings, which are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application. Fig. 1 shows a diagram of an exemplary system architecture to which the technical scheme of the embodiments of the present application can be applied; Fig. 2 schematically shows a flowchart of a character retrieval method according to an embodiment of the present application; Fig. 3 schematically shows a diagram of terminal interface switching involved in a character retrieval method according to an embodiment of the present application; Fig. 4 schematically shows a diagram of a display interface involved in a character retrieval method according to an embodiment of the present application; Fig. 5 schematically shows a diagram of a display interface involved in a character retrieval method according to an embodiment of the present application; Fig. 6 schematically shows a diagram of a display interface involved in a character retrieval method according to an embodiment of the present application; Fig. 7 schematically shows a diagram of a display interface involved in a character retrieval method according to an embodiment of the present application; Fig. 8 schematically shows a diagram of display interface switching involved in a character retrieval method according to an embodiment of the present application; Fig. 9 schematically shows a diagram of display interface switching involved in a character retrieval method according to an embodiment of the present application; Fig.10 schematically shows a block diagram of a character retrieval apparatus according to an embodiment of the present application; and Fig. 11 is a hardware diagram of an electronic device according to an exemplary embodiment. DETAILED DESCRIPTION Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, exemplary embodiments can be implemented in many forms and should not be construed as being limited to the examples set forth herein; on the contrary, these embodiments are provided to make the present application more comprehensive and complete, and to fully convey the concept of the example embodiments to those skilled in the art. In addition, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present application. However, those skilled in the art will realize that the technical scheme of the present application can be practiced without one or more of the specific details, or with other methods, components, devices, steps, etc. In other cases, well-known methods, devices, implementations or operations are not shown or described in detail to avoid obscuring aspects of the present application. The block diagrams shown in the drawings are only functional entities and do not necessarily correspond to physically separate entities. That is, these functional entities can be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different networks and/or processor devices and/or microcontroller devices. The flowchart shown in the drawings is only an exemplary illustration, and does not necessarily include all contents and operations/steps, nor do the operations/steps have to be executed in the described order. For example, some operations/steps can be decomposed, while some operations/steps can be combined or partially combined, so the actual execution order may change according to the actual situation. Fig. 1 shows a diagram of an exemplary system architecture 100 to which the technical scheme of the embodiments of the present application can be applied. As shown in Fig.1, the system architecture 100 may include a client 101, a network 102 and a server 103. The network 102 is a medium for providing a communication link between the client 101 and the server 103. The network 102 may have various connection types, such as a wired communication link and a wireless communication link, which is not limited herein. It should be understood that the number of the client(s) 101, the number of the network(s) 102 and the number of the server(s) 103 in Fig.1 are only schematic. There may be any number of the client(s) 101, network(s) 102 and server(s) 103 according to implementation requirements. For example, the server 103 may be an independent physical server, a server cluster composed of multiple physical servers or a distributed system, or may be a cloud server which provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, content delivery networks (CDN), and big data and artificial intelligence platforms. The client 101 may be a smart phone, a tablet computer, a laptop computer, a desktop computer, a smart speaker, a smart watch, a robot, etc., but is not limited thereto. In one embodiment of the present application, by acquiring a target stroke, retrieving candidate components containing the target stroke, and displaying the candidate components, the client 101 prompts a user to select a target component from the candidate components; by displaying the target component in response to the component selection instruction to select the target component from the candidate components, and displaying the at least one position selection button for selecting the position of the target component, the user is prompted to select the position of the target component; by acquiring the target position corresponding to the position selection instruction in response to the position selection instruction to select the position of the target component received through the at least one position selection button, and retrieving the candidate characters with the target component at the target position, the number of the candidate characters can be greatly reduced, and then the candidate characters are displayed, so that the user is prompted to select from the candidate characters the character to be retrieved; and the character to be retrieved is retrieved in response to the character selection instruction to select from the candidate characters the character to be retrieved. By displaying the candidate components, the position selection buttons and the candidate characters, the user can be prompted to give a selection instruction, thus reducing the difficulty of retrieving the character to be retrieved. In addition, the candidate characters are determined by the combination of the target component and the target position, and the position of the target component in the character to be retrieved is not limited, as long as the target component corresponds to the target position, which further reduces the difficulty of retrieving the character to be retrieved. In one embodiment of the present application, by acquiring the target stroke input by the user through the client 101, retrieving the candidate components containing the target stroke, sending the candidate components to the client 101, and displaying the candidate components in the client 101, the server 103 prompts the user to select the target component from the candidate components; by sending the target component to the client 101 and displaying the target component in the client 101 in response to the component selection instruction to select the target component from the candidate components input by the user through the client 101, and displaying the at least one position selection button for selecting the position of the target component in the client 101, the user is prompted to select the position of the target component; by acquiring the target position corresponding to the position selection instruction in response to the position selection instruction to select the position of the target component received through the at least one position selection button of the client 101, and retrieving candidate characters with the target component at the target position, the number of the candidate characters can be greatly reduced, and then the candidate characters are sent to the client 101 and displayed in the client 101, so that the user is prompted to select from the candidate characters the character to be retrieved; and the character to be retrieved is retrieved in response to the character selection instruction input by the user through the client 101 to select from the candidate characters the character to be retrieved. By displaying the candidate components, the position selection buttons and the candidate characters, the user can be prompted to give a selection instruction, thus reducing the difficulty of retrieving the character to be retrieved. In addition, the candidate characters are determined by the combination of the target component and the target position, and the position of the target component in the character to be retrieved is not limited, as long as the target component corresponds to the target position, which further reduces the difficulty of retrieving the character to be retrieved. It should be noted that the character retrieval method provided by the embodiment of the present application is generally executed by the client 101, and correspondingly, a character retrieval apparatus is generally installed in the client 101. However, in a further embodiment of the present application, the server 103 may also have similar functions as the client 101, so as to execute the character retrieval method provided by the embodiments of the present application. The implementation details of the technical scheme of the embodiment of the present application are described in detail below: Fig. 2 schematically shows a flowchart of a character retrieval method according to an embodiment of the present application. An executing subject of the character retrieval method may be a server, such as the client 101 shown in Fig.1. Referring to Fig. 2, the character retrieval method at least includes steps S210 to S240, which are described in detail as follows. In step S210, a target stroke is acquired, candidate components containing the target stroke are retrieved, and the candidate components are displayed. In one embodiment of the present application, the target stroke may be input by the user in the client 101, for example, the target stroke may be input by handwriting. The component may be the same as the stroke or a combination of multiple strokes. The component may be determined based on continuity, that is, strokes connected together may be determined as one component, so that users can easily use the method even if without having a good knowledge of radicals. In a further embodiment of the present application, the component may be a radical. In one embodiment of the present application, in response to a retrieval instruction, basic strokes may be acquired and displayed; and in response to a stroke selection instruction to select the target stroke from the basic strokes, the target stroke is acquired, the candidate components containing the target stroke are retrieved, and the candidate components are displayed. The retrieval instruction may be input in an interface shown in Fig.3 which schematically shows a diagram of terminal interface switching involved in a character retrieval method according to an embodiment of the present application. By tapping the GAMES button in the left figure of Fig. 3 which becomes darker after being selected, the interface in the right figure of Fig. 3 is presented, which confirms that the user has input the retrieval instruction. In one embodiment of the present application, the basic strokes may be preset. For example, when the character to be retrieved is a Chinese character, the basic strokes may include: a dot stroke (丶), a horizontal stroke (一), a vertical stroke (丨), a left-falling stroke ( 丿), a right-falling stroke (乀), a rising stroke ( ^), etc. In a further embodiment of the present application, the preset basic strokes may also be a dot stroke (丶), a horizontal stroke (一), a vertical stroke (丨) or a vertical-J hook stroke (亅), a left-falling stroke (丿) and a horizontal-J hook stroke (乛), as shown in Figs.4 and 7. Figs.4 and 7 are diagrams of a display interface involved in a character retrieval method according to an embodiment of the present application. In one embodiment of the present application, the target stroke and the basic strokes may be identified from the character to be retrieved. In one embodiment of the present application, a character image of the character to be retrieved may be acquired; the character image is segmented to obtain a plurality of image segments; a stroke in each image segment at a given position is acquired; and the basic strokes are determined based on the strokes at the given positions, where the position may include: the whole image, top, bottom, left, right, center, outside, left-top, right-top, left-bottom and right- bottom. In one embodiment of the present application, the character image of the character to be retrieved may be acquired after the character to be retrieved enters a visual range, or the character image of the character to be retrieved pre-stored in the client 101 may be acquired. In one embodiment of the present application, the character may be segmented based on the continuity between strokes. The stroke at the left-top, left or top of the image segment may be taken as the stroke at the given position. Stroke acquisition may be conducted in the order of left-top, left and top. That is, the stroke at the left-top may be acquired first; if the acquisition fails, the stroke at the left is to be acquired; and if the acquisition fails, the stroke at the top is to be acquired. The strokes in the image segments at the given positions may be taken as the basic strokes. In a further embodiment of the present application, a starting stroke in an image segment at a given image position in the character image and preset strokes related to the starting stroke may be taken as the basic strokes. For example, when the starting stroke in the segment image at the given image position in the character image is a horizontal stroke (一), the preset strokes related to the starting stroke may include: a dot stroke (丶), a vertical stroke (丨) or a vertical-J hook stroke (亅), a left-falling stroke (丿), and a horizontal-J hook stroke ( 乛). In one embodiment of the present application, the basic strokes may be displayed in a stroke display page to prompt the user to select the target stroke from the basic strokes. The basic strokes displayed in the stroke display page may be changeable. If a stroke change instruction instead of the stroke selection instruction is received, the basic strokes can be replaced with alternative basic strokes. The stroke change instruction may be to swipe horizontally or vertically on the page. In one embodiment of the present application, the candidate components may be retrieved in response to the stroke selection instruction received through the stroke display page; and the stroke selection page may be switched to the component selection page, the candidate components are displayed in the component selection page, and the user is prompted to finish stroke selection and start component selection through the page switching. The candidate components in the component selection page may also be changeable, so that all candidate components in one component selection page can be displayed. The candidate components may be changed in response to a component change instruction, as shown in Figs.5 and 8. Fig.5 is a schematic diagram of a display interface in a character retrieval method according to an embodiment of the present application. Fig. 8 is a schematic diagram of display interface switching involved in a character retrieval method according to an embodiment of the present application. In one embodiment of the present application, candidate components with the target stroke as the starting stroke may be retrieved. In this way, the number of components acquired may be greatly reduced compared with acquiring all components containing the target stroke, so that the selection of the target component can be accelerated. In one embodiment of the present application, a position of the target stroke in the candidate component may be selected, so as to determine the candidate component according to both the target stroke and the position of the target stroke. In one embodiment of the present application, if no candidate component is found, the target stroke is taken as the character to be retrieved; and if no candidate character is found, the target component is taken as the character to be retrieved. In step S220, in response to a component selection instruction to select a target component from the candidate components, the target component is displayed, and at least one position selection button for selecting a position of the target component is displayed. In one embodiment of the present application, in response to the component selection instruction received through the component selection page, the component selection page may be switched to a character selection page, so that the user is prompted to select characters through the page switching, and the target component and the position selection buttons are displayed in the character selection page, as shown in Figs. 6 and 9. Fig. 6 is a schematic diagram of a display interface in a character retrieval method according to an embodiment of the present application. Fig. 9 is a schematic diagram of display interface switching involved in a character retrieval method according to an embodiment of the present application. In one embodiment of the present application, when switching to the character selection page, the position selection buttons which receive a selected preset position may be set at the same time; when displaying the character selection page, the preset position may be acquired, preset characters with the target component at the preset position are retrieved, and the preset characters are displayed in the character selection page; and in response to the position selection instruction to select the target position at the position selection buttons, the candidate characters with the target component at the target position are retrieved, and in the character selection page, the preset characters are replaced with the candidate characters. In one embodiment of the present application, there may be more than one position selection button; after acquiring the preset position, one or more position selection buttons corresponding to the preset position may be marked in the character selection page; and after acquiring the position selection instruction, the one or more position selection buttons corresponding to the preset position are unmarked in the character selection page, and one or more position selection buttons corresponding to the position selection instruction are marked. Marking may be realized by differentiated display, for example, the marked button may be highlighted. In step S230, in response to a position selection instruction to select the position of the target component received through the at least one position selection button, a target position corresponding to the position selection instruction is acquired, candidate characters with the target component at the target position are retrieved, and the candidate characters are displayed. In one embodiment of the present application, one or more position selection buttons selected in the character selection page according to the position selection instruction may be acquired as the one or more position selection buttons corresponding to the position selection instruction; and a position of the one or more position selection buttons corresponding to the position selection instruction in the plurality of position selection buttons may be acquired as the target position, for example, when a button located at the “top” in the plurality of position selection buttons is selected, the target position may be determined as “top”. In one embodiment of the present application, the number of the position selection buttons is at least nine, and the position selection buttons are arranged into a square array. For example, when there are nine position selection buttons, the nine position selection buttons are arranged into a 3x3 square array to represent “inside”, “center” and “outside”. In this way, many positions may be represented. In one embodiment of the present application, the target position may be acquired by fuzzy matching. If there are nine position selection buttons, when the position selection buttons in the first column from the left are selected, the target position may be left or left-center, so that more potential candidate characters may be acquired. In one embodiment of the present application, if a stroke adding instruction is received, next candidate strokes in the same component as the target stroke are retrieved, and the next candidate strokes are displayed; in response to a next stroke selection instruction to select a next target stroke from the next candidate strokes, the next target stroke is acquired, and candidate components containing the target stroke and the next target stroke are retrieved; and the target stroke and the next target stroke are displayed, and the candidate components containing the target stroke and the next target stroke are displayed, which further reduces the number of the candidate components acquired, thus accelerating the retrieval speed. In one embodiment of the present application, before responding to the next stroke selection instruction, in response to the stroke adding instruction received through a stroke adding button, the target stroke may be moved away from a reserved position for displaying the next target stroke in a stroke display area, as shown in Fig. 8; in response to the next stroke selection instruction, the target stroke is displayed in the stroke display area, and the next target stroke is displayed at the reserved position in the stroke display area, so that strokes in the stroke display area can be displayed at proper positions, for example, when there is only the target stroke in a stroke selection area, the target stroke may be located in the center of the stroke display area; and when responding to the next stroke selection instruction, the target stroke is moved from the center to one side, such as the left side, and half of the stroke display area of another layer is taken as the reserved position of the next target stroke, and so on, in response to each stroke adding instruction, one stroke may be added, and the strokes are arranged in the stroke display area according to a stroke selection order, so that the user can quickly retrieve the character. In one embodiment of the present application, if a component adding instruction is received, a target stroke of a next component is acquired, next candidate components containing the target stroke of the next component are retrieved, and the next candidate components are displayed; in response to a component selection instruction to select a next target component from the next candidate components, the next target component is displayed, and at least one position selection button for selecting a position of the next target component is displayed; and in response to a position selection instruction to select the position of the next target component received through the at least one position selection button, a next target position corresponding to the position selection instruction is acquired, candidate characters with the target component at the target position and the next target component at the next target position are retrieved, and the candidate characters are displayed, where for the process of retrieving the next target component, one can refer to the process of retrieving the target component. In one embodiment of the present application, if no candidate character is found, the target component is taken as the character to be retrieved. Referring to Fig. 2 still, in step S240, in response to a character selection instruction to select from the candidate characters a character to be retrieved, the character to be retrieved is retrieved. In the embodiment shown in Fig.2, by acquiring the target stroke, retrieving the candidate components containing the target stroke, and displaying the candidate components, the user is prompted to select the target component from the candidate components; by displaying the target component in response to the component selection instruction to select the target component from the candidate components, and displaying the at least one position selection button for selecting the position of the target component, the user is prompted to select the position of the target component; by acquiring the target position corresponding to the position selection instruction in response to the position selection instruction to select the position of the target component received through the at least one position selection button, and retrieving the candidate characters with the target component at the target position, the number of the candidate characters can be greatly reduced, and then the candidate characters are displayed, so that the user is prompted to select from the candidate characters the character to be retrieved; and the character to be retrieved is retrieved in response to the character selection instruction to select from the candidate characters the character to be retrieved. By displaying the candidate components, the position selection buttons and the candidate characters, the user can be prompted to give a selection instruction, thus reducing the difficulty of retrieving the character to be retrieved. In addition, the candidate characters are determined by the combination of the target component and the target position, and the position of the target component in the character to be retrieved is not limited, as long as the target component corresponds to the target position, which further reduces the difficulty of retrieving the character to be retrieved. In one embodiment of the present application, retrieving a Chinese character by using the character retrieval method of the present application may include the following steps: Firstly, for the Chinese character to be retrieved entering a visual range, character image segmentation is conducted, and the character image is divided into image segments based on their connectivity. Then, the target stroke is determined (five basic stroke options are provided), and a starting stroke may be used as the target stroke, which only appears at three positions (left, top or left-top), and can be easily identified by a searcher. The components starting with this stroke are automatically listed, and the searcher selects the target component in a preset component library. If there are too many listed results that it is difficult to quickly locate the target component, a second stroke is selected according to a general rule of "first top, then bottom" and "first left, then right", the candidate components with the defined starting stroke and second stroke are automatically listed, and the searcher selects the target component in the component library. If there are still too many listed component results, a third stroke is searched for. Because the number of Chinese characters is limited, the target component will be retrieved eventually. Secondly, the component is located to the target position. The positions of the components of Chinese characters are very limited, including the whole picture, top, bottom, left, right, center, outside, left-top, right-top, left-bottom and right-bottom. The searcher moves the target component acquired from the previous step to the target position according to the pattern of the character. Thirdly, the present invention includes a Chinese character library, which lists all possible Chinese characters with the target component at the current position through automatic matching, and the searcher can find the target Chinese character in the listed results. If there are too many possible Chinese characters with the target component at the current position, the first and second steps are repeated, and then the searcher can find the target Chinese character from possible Chinese characters with two target components at the corresponding positions. Example scenario: One sees “中国盛产茶叶” when reading. The character to be retrieved is “茶”. First, the character is subjected to image segmentation. According to the connectivity- based general standard, the character is divided into “艹”, “人” and “木”. The left-top line of each segment obtained after segmentation is the starting stroke (stroke options are provided, 5 options in total), which is easy for the searcher to identify. A diagram of a terminal interface involved in a character retrieval method according to an embodiment of the present application is shown. In order to find the component “艹”, the searcher defines the starting stroke as “一”. A component library lists the following possible components:一,二,元,王,石,土, etc., as shown in Fig. 5. Fig. 5 is a diagram of a terminal interface involved in a character retrieval method according to an embodiment of the present application, where the target component “ 艹” is not listed. Then the searcher defines the second stroke “丨”. A component library lists the following possible components:十,土,古,艹, etc. The target component appears this time, and the searcher directly selects the target component “艹” and defines “艹” as a top component of the Chinese character based on a visual impression. In this case, a Chinese character library lists the following Chinese characters with “艹” on top:草,花,芝,荤,苛, 茜,芜, 莓, etc. But the target character is not included. So, the searcher keeps looking for the second component. In order to find the component “人”, the searcher defines the starting stroke as “丿”. A component library lists the following possible components:人,竹,夭,矢,彳,彡, etc. The target component appears, and the searcher directly selects the target component “人” and defines “人” as a center component of the Chinese character based on the visual impression. Based on the second component “人” and the first component “艹”, a Chinese character library lists the following Chinese characters:茶,苶,花,葆,荷, etc. The target Chinese character “茶” now appears. The apparatus embodiments of the present application will be described below, which can be used to carry out the character retrieval method in the above embodiments of the present application. For details not disclosed in the apparatus embodiments of the present application, please refer to the embodiments of the character retrieval method described above. Fig.10 schematically shows a block diagram of a character retrieval apparatus according to an embodiment of the present application. Referring to Fig.10, a character retrieval apparatus 1000 according to one embodiment of the present application includes an acquisition module 1001, a component selection module 1002, a position selection module 1003 and a character retrieval module 1004. According to one aspect of embodiments of the present application, based on the foregoing scheme, the acquisition module 1001 is configured to acquire a target stroke, retrieve candidate components containing the target stroke, and display the candidate components; the component selection module 1002 is configured to, in response to a component selection instruction to select a target component from the candidate components, display the target component, and display at least one position selection button for selecting a position of the target component; the position selection module 1003 is configured to, in response to a position selection instruction to select the position of the target component received through the at least one position selection button, acquire a target position corresponding to the position selection instruction, retrieve candidate characters with the target component at the target position, and display the candidate characters; and the character retrieval module 1004 is configured to, in response to a character selection instruction to select from the candidate characters a character to be retrieved, retrieve the character to be retrieved. In one embodiment of the present application, based on the foregoing scheme, the acquisition module 1001 is configured to: in response to a retrieval instruction, acquire basic strokes and display the basic strokes; and in response to a stroke selection instruction to select the target stroke from the basic strokes, acquire the target stroke, retrieve the candidate components containing the target stroke, and display the candidate components. In one embodiment of the present application, based on the foregoing scheme, before acquiring the basic strokes, the acquisition module 1001 is further configured to: acquire a character image of the character to be retrieved; segment the character image to obtain a plurality of image segments; acquire a stroke in each image segment at a given position; and determine the basic strokes based on the strokes at the given positions. In one embodiment of the present application, based on the foregoing scheme, the acquisition module 1001 is configured to: display the basic strokes in a stroke display page; in response to the stroke selection instruction received through the stroke display page, retrieve the candidate components; and switch from the stroke selection page to a component selection page, and display the candidate components in the component selection page. In one embodiment of the present application, based on the foregoing scheme, the component selection module 1002 is configured to: in response to the component selection instruction received through the component selection page, switch from the component selection page to a character selection page, and display the target component and the at least one position selection button in the character selection page; and acquire a preset position, retrieve preset characters with the target component at the preset position, and display the preset characters in the character selection page; and the position selection module is configured to: replace the preset characters with the candidate characters in the character selection page. In one embodiment of the present application, based on the foregoing scheme, a plurality of the position selection buttons are provided, and after obtaining the preset position, the component selection module 1002 is further configured to: mark in the character selection page one or more position selection buttons corresponding to the preset position; and after acquiring the position selection instruction, in the character selection page, unmark the one or more position selection buttons corresponding to the preset position, and mark one or more position selection buttons corresponding to the position selection instruction. In one embodiment of the present application, based on the foregoing scheme, the position selection module 1003 is configured to: acquire one or more position selection buttons selected in the character selection page according to the position selection instruction as the one or more position selection buttons corresponding to the position selection instruction; and acquire a position of the one or more position selection buttons corresponding to the position selection instruction in the plurality of position selection buttons as the target position. In one embodiment of the present application, based on the foregoing scheme, the number of the position selection buttons is at least nine, and the position selection buttons are arranged into a square array. In one embodiment of the present application, based on the foregoing scheme, the acquisition module 1001 is configured to: retrieve candidate components with the target stroke as a starting stroke. In one embodiment of the present application, based on the foregoing scheme, before responding to the component selection instruction, the component selection module 1002 is further configured to: if a stroke adding instruction is received, retrieve next candidate strokes in the same component as the target stroke, and display the next candidate strokes; in response to a next stroke selection instruction to select a next target stroke from the next candidate strokes, acquire the next target stroke, and retrieve candidate components containing the target stroke and the next target stroke; and display the target stroke and the next target stroke, and display the candidate components containing the target stroke and the next target stroke. In one embodiment of the present application, based on the foregoing scheme, before responding to the next stroke selection instruction, the component selection module 1002 is further configured to: in response to the stroke adding instruction received through a stroke adding button, move the target stroke away from a reserved position for displaying the next target stroke in a stroke display area; and in response to the next stroke selection instruction, display the target stroke in the stroke display area, and display the next target stroke in the reserved position in the stroke display area. In one embodiment of the present application, based on the foregoing scheme, before responding to the character selection instruction, the character retrieval module 1004 is further configured to: if a component adding instruction is received, acquire a target stroke of a next component, retrieve next candidate components containing the target stroke of the next component, and display the next candidate components; in response to a component selection instruction to select a next target component from the next candidate components, display the next target component, and display at least one position selection button for selecting a position of the next target component; and in response to a position selection instruction to select the position of the next target component received through the at least one position selection button, acquire a next target position corresponding to the position selection instruction, retrieve candidate characters with the target component at the target position and the next target component at the next target position, and display the candidate characters. Those skilled in the art can understand that individual aspects of the present application may be implemented as systems, methods or program products. Accordingly, aspects of the present application may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” An electronic device 1100 according to this embodiment of the present application will be described below with reference to Fig.11. The electronic device 1100 shown in Fig.11 is just an example and should not limit the scope of functions and application of the embodiments of the present application. As shown in Fig. 11, the electronic device 1100 is in the form of a general-purpose computing device. Components of the electronic device 1100 may include but are not limited to: at least one processing unit 1101, at least one storage unit 1102, a bus 1103 connecting different components (including the storage unit 1102 and the processing unit 1101), and a display unit 1104. Here, the storage unit stores program codes which may be executed by the processing unit 1101 to enable the processing unit 1101 to perform the steps according to various exemplary embodiments of the present application described in the “method embodiments” of this specification. The storage unit 1102 may include a computer-readable medium in the form of a volatile memory, such as a random access memory (RAM) 1121 and/or a cache memory 1122, and may further include a read-only memory (ROM) 1123. The storage unit 1102 may also include a program/utility tool 1124 with a set of (at least one) program modules 1125, such program modules 1125 include but are not limited to: an operation system, one or more application programs, other program modules and program data, and each or some combinations of these examples may include the implementation of a network environment. The bus 1103 may represent one or more of several types of bus structures, including a memory bus or a memory controller, a peripheral bus, an accelerated graphics port, a processing unit or a local bus using any of a variety of bus structures. The electronic device 1100 may also communicate with one or more external devices (such as a keyboard, a pointing device, a Bluetooth device, etc.), one or more devices that enable users to interact with the electronic device 1100, and/or any device that enables the electronic device 1100 to communicate with one or more other computing devices (such as a router, a modem, etc.). This kind of communication can be done through an input/output (I/O) interface 1105. Furthermore, the electronic device 1100 may also communicate with one or more networks (such as a local area network (LAN), a wide area network (WAN), and/or a public network such as the Internet) through a network adapter 1106. As shown, the network adapter 1106 communicates with other modules of the electronic device 1100 through the bus 1103. It should be understood that although not shown in the figures, other hardware and/or software modules can be used in conjunction with the electronic device 1100, including but not limited to: microcode, a device driver, a redundant array of independent disks (RAID) system, a tape drive and a data backup storage system, etc. From the above description of the embodiments, it is easy for those skilled in the art to understand that the exemplary embodiments described herein may be implemented in software or software combined with necessary hardware. Therefore, the technical schemes according to the embodiments of the present application may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (which may be a CD-ROM, USB flash drive, mobile hard drive, etc.) or on a network, and may include several instructions to enable a computing device (which may be a personal computer, server, terminal device, or network device, etc.) to execute the method according to the embodiments of the present application. According to one embodiment of the present application, there is also provided a computer-readable storage medium that stores a program product capable of implementing the method described above in the specification. In some possible embodiments, individual aspects of the application may also be embodied in the form of a program product including program code, which, when executed on a terminal device, causes the terminal device to perform the steps according to various exemplary embodiments of the present application described in the above “exemplary methods” section herein. According to an embodiment of the present application, the program product for realizing the above method may be a portable compact disk read-only memory (CD-ROM) and include program codes, and can be run on a terminal device such as a personal computer. However, the program product of the present application is not limited to this. Herein, the readable storage medium may be any tangible medium containing or storing a program, which can be used by or in combination with an instruction execution system, apparatus or instrument. The program product may use any combination of one or more computer-readable media. The computer-readable medium can be a computer-readable signal medium or a computer- readable storage medium. A computer-readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random-access memory (RAM), a read-only memory (ROM), an erasable programmable read- only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. A computer-readable signal medium may include a propagated data signal with computer- readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer-readable signal medium may be any computer-readable medium that is not a computer-readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer-readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. Computer program code for carrying out operations of the present application may be written in any combination of one or more programming languages, including an object- oriented programming language such as Java, C++, or the like, and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on a remote computer or server. In the latter scenario involving a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In addition, the above drawings are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present application, and are not intended to be limiting. It is easy to understand that the processes shown in the above drawings do not indicate or limit a chronological order of these processes. In addition, it is also easy to understand that these processes may be executed synchronously or asynchronously, for example, in a plurality of modules. It is to be understood that the present application is not limited to the precise structures described above and shown in the accompanying drawings, and modifications and changes can be made without departing from the scope of the present application. The scope of the present application is limited only by the appended claims.