leetcode[24]:Swap Nodes in Pairs

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; *     struct ListNode *next; * }; */struct ListNode* swapPairs(struct ListNode* head) {    int tmp;    struct ListNode* l;    l=head;    if(!head || !head->next) return head;    while(l->next)    {        tmp=l->val;        l->val=l->next->val;        l->next->val=tmp;        l=l->next->next;        if(!l) break;    }    return head;}

两两交换，没有什么难度。