头节点单链表

直接上代码

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

typedef struct list{
    int num;
    struct list *next;
}list_t;


//链表头初始化
list_t *list_init()
{
    list_t *head = (list_t *)malloc(sizeof(list_t));
    if(head == NULL)
        return NULL;
    
    head->num = 0;
    head->next = NULL;

    return head;
}


//尾部追加
void append_tail(list_t *h,int num)
{
    list_t *one = (list_t *)malloc(sizeof(list_t));
    if(one == NULL)
        return;
    
    one->num = num;
    one->next = NULL;

#if 1
    list_t *end;
    end = h;
    while(end->next != NULL)
        end = end->next;
    
    end->next = one;
#else
    //二级指针尾部追加
    list_t **link;
    link = &h->next;
    while(*link)
        link = &(*link)->next;
    
    *link = one;
#endif
}


//头部追加
void append_top(list_t *h,int num)
{
    list_t *one = (list_t *)malloc(sizeof(list_t));
    if(one == NULL)
        return;
    
    one->num = num;
    
    //以下两行不可调换，防止无节点时产生错误
    one->next = h->next;
    h->next = one;
}


//遍历链表
void trave_list(list_t *h)
{
    list_t *i;
    
    for(i=h->next;i!=NULL;i=i->next)
        printf("%x ",i->num);
    
    printf("\n");
}


//删除链表
void delete_list(list_t *h)
{
#if 0
    list_t *i;
    list_t *j;

    for(i=h->next;i!=NULL;i=j)
    {
        j = i->next;
        h->next = i->next;
        free(i);
    }
#else
    //二级指针删除链表
    list_t *entry;
    list_t **link = &h->next;
    while(*link)
    {
        entry = *link;
        #if 0
        //删除所有节点
        *link = entry->next;    //将头节点指向<删除节点>的后一个节点
        free(entry);
        #else
        //一个节点不删除
        link = &entry->next;
        #endif
    }
#endif
}


int main()
{
    int num = 0;
    list_t *head = list_init();

    while(1)
    {
        scanf("%d",&num);
        if(num == -1)
            break;
        
        append_tail(head,num);
    }

    trave_list(head);

    delete_list(head);

    trave_list(head);

    return 0;
}