单链表双指针实现

单链表的实现思想和双指针的应用方法在前面博客中都已阐述，在本文将实现双指针实现单链表的初始化，插入，删除，打印。
【测试代码1】

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

typedef  struct Node{
    int data;
    struct Node *next;
}node_t;

//创建头结点
node_t * create()
{
    node_t *head = (node_t *)malloc(sizeof(node_t));
    head->next = NULL;

    return head;
}
void insert(node_t **list, int data)
{
    node_t *pnode = (node_t *)malloc(sizeof(pnode));
    pnode->data = data;
    pnode->next = NULL;

    if(*list == NULL)
    {
        *list = pnode;
    }
    else
    { 
        node_t *p =*list;
        while(p->next != NULL)
        {
            p = p->next;
        }
        p->next = pnode;
    }
}

void remove(node_t **list, int data)
{
    node_t *p =( *list);

    if(p ->next== NULL)
        return ;
    while(p->next->data != data)
        p = p->next;
    if(p->next == NULL)
        printf("no data");
    if (p->next->data == data)
        p->next = p->next->next;

}

void print(node_t **list)
{

    node_t *p = (*list)->next;

    if(!p)
        return;
    while(p != NULL)
    {
        printf("%d ",p->data);
        p = p->next;
    }

}
void main()
{

    node_t *head;//链表头结点
    node_t **list;//链表头指针
    head = create();
    list =& head;//令链表头指针指向头结点
    insert(list,1);
    insert(list,2);
    insert(list,3);
    insert(list,4);
    insert(list,5);
    insert(list,6);
    printf("after insert data, the list data is:\n");
    print(list);
    printf("\n");
    printf("remove data 6, the list data is:\n");
    remove(list,6);
    print(list);
}

【输出结果】

这里采用尾部插入，所以头指针始终指向头结点，双指针的用处就是你可以改变其头结点后面的内容，而不会改变头指针的位置，如果是前部插入的话，需要不断变化头结点的位置，程序会有所区别。
【测试代码2】

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

typedef  struct Node{
    int data;
    struct Node *next;
}node_t;

//使得头指针指向头结点
node_t * create()
{
    node_t *head = (node_t *)malloc(sizeof(node_t));
    head->next = NULL;

    return head;
}
void insert_front(node_t **list, int data)
{
    node_t *pnode = (node_t *)malloc(sizeof(pnode));
    pnode->data = data;
    pnode->next = (*list)->next;
    (*list)->next = pnode;
}

void remove(node_t **list, int data)
{
    node_t *p =( *list);

    if(p ->next== NULL)
        return ;
    while(p->next->data != data)
        p = p->next;
    if(p->next == NULL)
        printf("no data");
    if (p->next->data == data)
        p->next = p->next->next;

}

void print(node_t **list)
{

    node_t *p = (*list)->next;

    if(!p)
        return;
    while(p != NULL)
    {
        printf("%d ",p->data);
        p = p->next;
    }

}
void main()
{

    node_t *head;
    node_t **list;
    head = create();
    list =& head;
    insert_front(list,1);
    insert_front(list,2);
    insert_front(list,3);
    insert_front(list,4);
    insert_front(list,5);
    insert_front(list,6);
    printf("after insert data, the list data is:\n");
    print(list);
    printf("\n");
    printf("remove data 6, the list data is:\n");
    remove(list,6);
    print(list);
}

【输出结果】