LC 206. Reverse Linked List

题目描述

Reverse a singly linked list.

Example:

Input: 1->2->3->4->5->NULL
Output: 5->4->3->2->1->NULL

参考答案

 /**
  * 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* cur = NULL;
         while(head){
             ListNode * temp = head->next;
             head -> next = cur;
             cur = head;
             head = temp;
         }
         return cur;
     }
 };

补充说明

term 1:

temp = 2 3 4 5 null

head = 1 null = 1 2 3 4 5 null + null

cur = 1 null

head = 2 3 4 5 null

term 2:

temp = 3 4 5 null

head = 2 1 null （ 2 3 4 5 null + 1 null）

cur = 2 1 null

head = 3 4 5 null

term 3:

temp = 4 5 null

head = 3 2 1 null = 3 4 5 null + 2 1 null

cur = 3 2 1 null

head = 4 5 null

......