链表逆序

链表逆序思路分析：

（1）如果链表为NULL，则不需要逆序

（2）不为空的话就，则设置三个指针，一个为current，一个为pnext，pnext（current->next）为current的后继，另外一个prev（current->next->next）为pnext的后继

（3）循环current和pnext指针，直到penxt为空

（4）重新设置头指针，指向链表最后的一个节点

图示分析：

 没逆序之前：

第一次变换：

 

第二次变换：

第三次变换：

 

重新设置头指针：

 

代码分析：

//链表逆序
void reverse(node *head)
{
    node *pnext,*current,*prev; 
     if(head == NULL || head->next == NULL) //空链表
         return;
     current = head->next; //current初始化指向头节点
     pnext = current->next; //pnext初始化指向头节点的后继节点
     current->next = NULL; //把头节点的指针域初始化为空
    
    while(pnext)
    {
        prev = pnext->next; //current->next->next
        pnext->next = current;  //后一个节点指向前一个节点实现逆序
        current = pnext; //current向后移动
        pnext = prev; //pnext向后移动
    }
    head->next = current; //重新设置头节点，形成逆序的链表
}

源代码：

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

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

//初始化链表头
node* inti(node* head)
{
    head = (node*)malloc(sizeof(node));
    head->data = 0;
    head->next = NULL;
    return head;
}

//插入生成节点
void create_new_node(node* head,int data)
{
    node* new = (node*)malloc(sizeof(node));
    node* p;
    p = head;
    new->data = data;
    if(head->next == NULL)
    {
        head->next = new;
        new->next = NULL;
    }
        
    else
    {
        while(p->next)
            p = p->next;
        p->next = new;
        new->next = NULL;
    }
  
}

//显示链表
void display(node *head)
{
    printf("the list node data:\n");
    node *p;
    p = head->next;
    while(p)
    {
        printf("%d\n",p->data);
        p = p->next;
    }
       
}

//删除节点
void delete_node(node* head,int data)
{
    node *p,*q;
    p = head;
    q = p;
    while(p)
    {
        if(p->next->data == data)
        {
            q->next = p->next->next;    
            break;
        }
        
        p = p->next;
        q = p;
    }
    
}

//链表逆序
void reverse(node *head)
{
    node *pnext,*current,*prev; 
     if(head == NULL || head->next == NULL) //空链表
         return;
     current = head->next; //current初始化指向头节点
     pnext = current->next; //pnext初始化指向头节点的后继节点
     current->next = NULL; //把头节点的指针域初始化为空
    
    while(pnext)
    {
        prev = pnext->next; //current->next->next
        pnext->next = current;  //后一个节点指向前一个节点实现逆序
        current = pnext; //current向后移动
        pnext = prev; //pnext向后移动
    }
    head->next = current; //重新设置头节点，形成逆序的链表
}

//销毁链表
void destroy(node *head)
{
    if(head->next == NULL)
        return;
    node *p,*q;
    p = head->next;
    while(p)
    {
        q = p;
        free(q);
        q->next = NULL;
        p = p->next;
    }
    free(head);
    
}

int main(int argc,char *argv[])
{
    node *head;
    head = inti(head);
    printf("create new node ,input 0 to qiut!!\n");
    int data;
    while(1)
    {
        scanf("%d",&data);
        if(data == 0)
            break;
        create_new_node(head,data);
    }
    display(head);
    printf("please input integer which you want to delete:");
    scanf("%d",&data);
    delete_node(head,data);
    display(head);
    printf("after reverse:\n");
    reverse(head);
    display(head);
    printf("free list:\n");
    destroy(head);
    display(head);
    return 0;
}

运行结果：