【12_206】Reverse Linked List

本来没想出来，刚才突然想到，可以用“头插法”来反转

Reverse Linked List

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Question

Total Accepted: 66556 Total Submissions: 182891 Difficulty: Easy

Reverse a singly linked list.

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Discuss中的递归解法：

 public ListNode reverseList(ListNode head) {
     return reverseListInt(head, null);
 }

 public ListNode reverseListInt(ListNode head, ListNode newHead) {
     if(head == null)
         return newHead;
     ListNode next = head.next;
     head.next = newHead;
     return reverseListInt(next, head);
 }

我的代码：用的是迭代（即循环）的方法

C语言：

 /**
  * Definition for singly-linked list.
  * struct ListNode {
  *     int val;
  *     struct ListNode *next;
  * };
  */
 struct ListNode* reverseList(struct ListNode* head) {
     if (head == NULL || head->next == NULL)
         return head;
     struct ListNode* p = head->next;
     struct ListNode* q = p;
     head->next = NULL;
     while(p)    {
         p = p->next;
         q->next = head;
         head = q;
         q = p;
     }

     return head;
 }