LeetCode题解：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.

题意：给定一个链表，成对交换邻接的节点

解决思路：每次移动节点向前移动两位，然后交换就可以了

代码：

public class Solution {
    public ListNode swapPairs(ListNode head) {
        ListNode newHead = new ListNode(0);
        newHead.next = head;

        for(ListNode curr = newHead; curr.next != null && curr.next.next != null; curr = curr.next.next){
            curr.next = swap(curr.next, curr.next.next);
        }

        return newHead.next;
    }

    private ListNode swap(ListNode prev, ListNode after){
        prev.next = after.next;
        after.next = prev;

        return after;
    }
}