Reverse Linked List[LeetCode]

Reverse a singly linked list.

click to show more hints.

Hint:
A linked list can be reversed either iteratively or recursively. Could you implement both?
题目要求：反转单链表
通过在反转过程中保存临时节点的方式对链表进行反转
遇到问题主要有：在节点建立后需要进行节点的内存分配申请，在C语言当中采用malloc的方式
如：新建一个结构体节点 ListNode* node; node = (ListNode*)malloc(sizeof(ListNode));
在c++当中可通过new的方式去申请内存分配，如ListNode* node = new ListNode;
c++代码：
#include<cstdio>
#include<cstring>
#include<string>
#include<cstdlib>
#include<map>
#include<iostream>
using namespace std;
struct ListNode {
int val;
ListNode *next;
};
class Solution {
public:
ListNode* reverseList(ListNode* head) {
if(head == NULL || head->next == NULL){
return head;
}
ListNode* pre = head;
ListNode* next = head->next;
ListNode* nextNext = head->next->next;
pre->next = NULL;
while(next)
{
nextNext = next->next;
next->next = pre;
pre = next;
next = nextNext;
}
return pre;
}
};
ListNode* createListNode()
{
ListNode* node1 = new ListNode;
node1->val = 1;
ListNode* node2 = new ListNode;
node2->val = 2;
node1->next = node2;
ListNode* node3 = new ListNode;
node3->val = 3;
node2->next = node3;
node3->next = NULL;
return node1;
}
int main()
{
ListNode* head = new ListNode;
ListNode* node = new ListNode;
head = createListNode();
node = head;
while(node)
{
cout << node->val << " ";
node = node->next;
}
cout << endl;
Solution s;
node = s.reverseList(head);
while(node)
{
cout << node->val << " ";
node = node->next;
}
cout << endl;
}