[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.

题解：

code：

 public ListNode swapPairs(ListNode head) {         ListNode p = new ListNode(0); p.next = head; ListNode tmp = p,curr = p; while(curr.next!=null && curr.next.next!=null){ tmp = curr.next; curr.next = tmp.next; tmp.next = curr.next.next; curr.next.next = tmp; curr = tmp; } return p.next; }