Swap Nodes in Pairs

題目描述

Given a linked list, swap every two adjacent nodes and return its head.You may not modify the values in the list’s nodes, only nodes itself may be changed. 
(給出一個鏈表，交換每兩個相鄰的節點並返回鏈表首節點。你可能不能改變lists的值，智能改變節點自身)
Example:

Given 1->2->3->4, you should return the list as 2->1->4->3.

題目分析

對鏈表進行遍歷，只遍歷其中的奇數節點，然後和它的next節點進行交換。

程序示例

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var swapPairs = function(head) {
    var cur = head
    while(cur){
        var tmp = cur.val
        if(cur.next){
            cur.val = cur.next.val
            cur.next.val = tmp
        }
        if(!cur.next){
            break
        }
        cur = cur.next.next
    }
    return head
};