C语言中的泛型链表-yiteyi-C++库

不像 C++ 和 JAVA , C 不支持泛型。如何在C语言中创建一个可用于任何数据类型的链表？在C中，我们可以使用空指针以及实现相同功能的函数指针。void指针的优点在于它可以用来指向任何数据类型。而且，所有类型指针的大小都是相同的，所以我们总是可以分配一个链表节点。需要函数指针来处理存储在void指针所指地址的实际内容。

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下面是一个示例C代码，用于演示通用链表的工作原理。

C

                         // C program for generic linked list                       
                         #include<stdio.h>                       
                         #include<stdlib.h>                       
           
                         /* A linked list node */                       
                         struct                                     Node                       
                         {                       
                                                 // Any data type can be stored in this node                       
                                                 void                                     *data;                       
           
                                                 struct                                     Node *next;                       
                         };                       
           
                         /* Function to add a node at the beginning of Linked List.                       
                                                 This function expects a pointer to the data to be added                       
                                                 and size of the data type */                       
                         void                                     push(                                     struct                                     Node** head_ref,                                     void                                     *new_data,                                     size_t                                     data_size)                       
                         {                       
                                                 // Allocate memory for node                       
                                                 struct                                     Node* new_node = (                                     struct                                     Node*)                                     malloc                                     (                                     sizeof                                     (                                     struct                                     Node));                       
           
                                                 new_node->data  =                                     malloc                                     (data_size);                       
                                                 new_node->next = (*head_ref);                       
           
                                                 // Copy contents of new_data to newly allocated memory.                       
                                                 // Assumption: char takes 1 byte.                       
                                                 int                                     i;                       
                                                 for                                     (i=0; i<data_size; i++)                       
                                                 *(                                     char                                     *)(new_node->data + i) = *(                                     char                                     *)(new_data + i);                       
           
                                                 // Change head pointer as new node is added at the beginning                       
                                                 (*head_ref)    = new_node;                       
                         }                       
           
                         /* Function to print nodes in a given linked list. fpitr is used                       
                                                 to access the function to be used for printing current node data.                       
                                                 Note that different data types need different specifier in printf() */                       
                         void                                     printList(                                     struct                                     Node *node,                                     void                                     (*fptr)(                                     void                                     *))                       
                         {                       
                                                 while                                     (node != NULL)                       
                                                 {                       
                                                 (*fptr)(node->data);                       
                                                 node = node->next;                       
                                                 }                       
                         }                       
           
                         // Function to print an integer                       
                         void                                     printInt(                                     void                                     *n)                       
                         {                       
                                                 printf                                     (                                     " %d"                                     , *(                                     int                                     *)n);                       
                         }                       
           
                         // Function to print a float                       
                         void                                     printFloat(                                     void                                     *f)                       
                         {                       
                                                 printf                                     (                                     " %f"                                     , *(                                     float                                     *)f);                       
                         }                       
           
                         /* Driver program to test above function */                       
                         int                                     main()                       
                         {                       
                                                 struct                                     Node *start = NULL;                       
           
                                                 // Create and print an int linked list                       
                                                 unsigned int_size =                                     sizeof                                     (                                     int                                     );                       
                                                 int                                     arr[] = {10, 20, 30, 40, 50}, i;                       
                                                 for                                     (i=4; i>=0; i--)                       
                                                 push(&start, &arr[i], int_size);                       
                                                 printf                                     (                                     "Created integer linked list is "                                     );                       
                                                 printList(start, printInt);                       
           
                                                 // Create and print a float linked list                       
                                                 unsigned float_size =                                     sizeof                                     (                                     float                                     );                       
                                                 start = NULL;                       
                                                 float                                     arr2[] = {10.1, 20.2, 30.3, 40.4, 50.5};                       
                                                 for                                     (i=4; i>=0; i--)                       
                                                 push(&start, &arr2[i], float_size);                       
                                                 printf                                     (                                     "Created float linked list is "                                     );                       
                                                 printList(start, printFloat);                       
           
                                                 return                                     0;                       
                         }                       

输出：

Created integer linked list is 10 20 30 40 50Created float linked list is 10.100000 20.200001 30.299999 40.400002 50.500000

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