leetcode 206. Reverse Linked List 反转字符串

Reverse a singly linked list.

反转链表，我这里是采用头插法来实现反转链表。

代码如下：

/*class ListNode
{
      int val;
      ListNode next;
      ListNode(int x) { val = x; }
}
*/
public class Solution
{ 
  public ListNode reverseList(ListNode head)
    {
        if(head==null || head.next==null)
            return head;

        ListNode newHead=new ListNode(0);
        newHead.next=head;
        ListNode start=newHead.next;

        while(start.next!=null)
        {
            ListNode then=start.next;
            start.next=then.next;
            then.next=newHead.next;
            newHead.next=then;
        }
        return newHead.next;    
    }    
}

下面是C++的做法，就是使用头部插入法来实现链表反转

代码如下：

#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <cmath>
#include <queue>
#include <stack>
#include <algorithm>

using namespace std;


/*
struct ListNode 
{
     int val;
     ListNode *next;
     ListNode(int x) : val(x), next(NULL) {}
};
*/

class Solution 
{
public:
    ListNode* reverseList(ListNode* h) 
    {
        if (h == NULL || h->next == NULL)
            return h;

        ListNode* head = new ListNode(-1);
        head->next = h;

        ListNode* i = h->next;
        ListNode* fa = h;
        while (i != NULL)
        {
            fa->next = i->next;
            ListNode* tmp = i;
            i = i->next;
            tmp->next = head->next;
            head->next = tmp;
        }
        return head->next;
    }
};