C语言笔记31 •单链表经典算法OJ题-3.反转链表•

反转链表

1.问题

给你单链表的头节点 head，请你反转链表，并返回反转后的链表。

2.代码实现：

//3.反转链表
#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>typedef int SLTDataType;typedef struct SListnode
{SLTDataType val;struct SListnode* next;
}ListNode;ListNode* createNode(SLTDataType val)
{ListNode* newnode = (ListNode*)malloc(sizeof(ListNode));if (newnode == NULL){perror("malloc");exit(1);}newnode->val = val;newnode->next = NULL;return newnode;
}struct ListNode* reverseList(struct ListNode* head)
{if (head == NULL){return head;}ListNode* n1,*n2,*n3 ;n1= NULL, n2=head, n3=n2->next;//创建三个节点while (n2){n2->next = n1;// 指针逆向n1 = n2;n2 = n3;if (n3){n3 = n3->next;}}return n1;
}int main()
{ListNode* node1, * node2, * node3, * node4, * node5;node1 = createNode(1);node2 = node1->next = createNode(2);node3 = node2->next = createNode(3);node4 = node3->next = createNode(4);node5 = node4->next = createNode(5);//创建一个链表ListNode* newhead = reverseList(node1);//反转链表while (newhead){printf("%d ", newhead->val);newhead = newhead->next;}return 0;
}