C中的通用链接列表

与C++和Java不同，C不支持泛型。如何在C中创建可用于任何数据类型的链表?在C语言中，我们可以使用void指针和函数指针来实现相同的功能。空指针的伟大之处在于它可以用于指向任何数据类型。另外，所有类型的指针的大小始终是相同的，因此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指针指向的地址中的实际内容。

以下是一个示例C代码，以演示通用链表的工作。

// C program for generic linked list
#include
#include
  
/* 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; idata + 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 \n");
    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("\n\nCreated float linked list is \n");
    printList(start, printFloat);
  
    return 0;
}

输出：

Created integer linked list is
 10 20 30 40 50

Created float linked list is
 10.100000 20.200001 30.299999 40.400002 50.500000

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