leetcode交换相邻的两个节点的值

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.

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这个也就是改天两个相邻的节点的值
这段代码使用的试类似交换两个数的值，然后使用了递归，

代码：

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