leetcode 206: Reversing a linked list

Title: Reverse Linked List

• Topic description:
  Reverse a singly linked list.

Advanced:
Linked lists can be reversed iteratively or recursively. Can you do both?

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        ListNode *new_head = NULL;  //指向新链表头节点的指针
        while(head){
            ListNode *next = head->next; //备份head->next
            head->next = new_head; //更新head->next
            new_head = head; //移动new_head
            head = next;  //遍历链表
        }
        return new_head; //返回新链表头节点
    }
};