Given a linked list, swap every two adjacent nodes and return its head.
For example,
Given1->2->3->4, you should return the list as2->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.
更改指针，即可。public ListNode swapPairs(ListNode head) { if(head == null || head.next == null){ return head; }else{ ListNode first = null; ListNode second = null; ListNode suc = null; ListNode pre = null; first = head; head = null; while(first.next != null){ second = first.next; suc = second.next; if(pre == null){ head = second; second.next = first; first.next = suc; pre = first; }else{ pre.next = second; second.next = first; first.next = suc; pre = first; } first = suc; if(first == null){ break; } } return head; } }
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原文：http://blog.csdn.net/u010378705/article/details/31371043