LeetCode---Swap Nodes in Pairs

Given a linked list, swap every two adjacent nodes and return its head.

For example,
Given 1->2->3->4, you should return the list as 2->1->4->3.

Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution 
{
public:
    ListNode *swapPairs(ListNode *head) 
    {
        if(head == NULL || head->next == NULL)
            return head;
        ListNode* first = head;
        ListNode* last = head->next;
        first->next = swapPairs(last->next);
        last->next = first;
        return last;
    }
};

LeetCode---Swap Nodes in Pairs

原文：http://blog.csdn.net/shaya118/article/details/42582035