Ｃ语言实现单链表逆置

思路：

使用三个指针，pre指向第一个结点，cur指向要逆置的结点，rear指向逆置结点后边的结点，循环条件为逆置结点存在，reverse函数实现逆置。

下面是实现的代码：

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

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


void add ( node**Head, int number );
void print ( node *Head );
void fre ( node *Head );
void reverse ( node **Head );

int main()
{
   
    int number;
    node *head = NULL;

    do {
   
        scanf("%d", &number);
        if ( number != -1 ) {
   
            add(&head, number);
        }
    }while( number != -1 );　　
　
    print(head);
    reverse(&head);
    print(head);
    fre(head);
	
	return 0;
	
}

//使用尾插法添加结点
void add ( node**Head, int number )
{
   
    node *p = (node*)malloc(sizeof(node));
    node *last = *Head;

    p->value = number;
    p->next = NULL;

    if ( last ) {
   
        while ( last->next ) {
   
            last = last->next;
        }
        last->next = p;
    }

    else {
   
        *Head = p;　　//要改变一个指针就要向函数中传入指针的指针，所以参数用了二级指针
    }
}

void print ( node *Head )
{
   
    node *p = Head;
    while ( p ) {
   
        printf("%d\n", p->value);
        p = p->next;
    }
}

void fre ( node *Head )
{
   
    node *p = Head, *q;
    
    while ( p ) {
   
        q = p;
        p = p->next;
        free(q);
    }
}

void reverse ( node **Head )
{
   
    node *pre = *Head, *cur, *rear, *p = *Head;

    if ( pre == NULL || pre->next == NULL )
        return ; 

    cur = pre->next;

    while ( cur ) {
   
        rear = cur->next;
        cur->next = pre;
        pre = cur;
        cur = rear;
    }
    p->next = NULL;　　　//实现逆置后让原来的头结点也就是现在的尾结点的next指针指向ＮＵＬＬ
    *Head = pre;　　　　 
}