Leetcode 24 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.

从头开始交换相邻节点的位置。

easy，来一波短码之美！

/** * 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* p=head->next;        head->next=swapPairs(p->next);        p->next=head;        return p;    }};