Reverse a linked list ＜ difficulty coefficient ＞

Title Description ： Here's the head node of the list head , Please reverse the list , And return the inverted linked list .

Example 1：
Input ：head = [1,2,3,4,5]
Output ：[5,4,3,2,1]

Example 2：
Input ：head = [1,2]
Output ：[2,1]

Example 3：
Input ：head = [ ]
Output ：[ ]

🧷 platform ：Visual studio 2017 && windows

The core idea ：
Ideas 1, Adjust the direction of the node pointer

Ideas 2, Head insertion

#include<stdio.h>#include<stdlib.h>typedef int SLTDataType;struct ListNode{	int val;	struct ListNode *next;};// Ideas 1struct ListNode* reverseList1(struct ListNode* head){	// Empty list     if(head == NULL)        return head;    struct ListNode* n1, *n2, *n3;    n1 = NULL;    n2 = head;    n3 = head->next;    while(n2)    {        n2->next = n1;        n1 = n2;        n2 = n3;        // The last time I came in ,n3 Null pointer         if(n3)            n3 = n3->next;    }    return n1;}// Ideas 2struct ListNode* reverseList2(struct ListNode* head){	struct ListNode *newnode, *cur, *next;    newnode = NULL;    cur = head;    while(cur)    {        next = cur->next;           cur->next = newnode;        newnode = cur;        cur = next;    }    return newnode;}int main(){	struct ListNode* n1 = (struct ListNode*)malloc(sizeof(struct ListNode));	n1->val = 1;	struct ListNode* n2 = (struct ListNode*)malloc(sizeof(struct ListNode));	n2->val = 2;	struct ListNode* n3 = (struct ListNode*)malloc(sizeof(struct ListNode));	n3->val = 3;	struct ListNode* n4 = (struct ListNode*)malloc(sizeof(struct ListNode));	n4->val = 4;	struct ListNode* n5 = (struct ListNode*)malloc(sizeof(struct ListNode));	n5->val = 5;		n1->next = n2;	n2->next = n3;	n3->next = n4;	n4->next = n5;	n5->next = NULL;		reverseList1(n1);	reverseList2(n1);	return 0;}