Swap Nodes in Pairs Java

最新推荐文章于 2019-05-12 11:43:46 发布

Spencer_Lin

最新推荐文章于 2019-05-12 11:43:46 发布

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分类专栏： LeetCode LinkedList 文章标签： leetcode

本文链接：https://blog.youkuaiyun.com/linxiang0591/article/details/37761723

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本文介绍了一种在常数空间复杂度下交换链表中每两个相邻节点的方法。通过使用虚拟头节点简化边界条件处理，并利用三个指针进行节点交换，确保仅修改节点指向而非节点值。

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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.

Have you been asked this question in an interview?

Goal: Swap adjacent node
Idea: 3 Nodes dummy, tempDummy, cur
1. swap each two adjacent nodes one by one by using tempDummy & cur
2. after swap, move both nodes forward to next adjacent pairs

public class Solution {
    public ListNode swapPairs(ListNode head) {
        if(head==null || head.next==null) return head;
        ListNode dummy=new ListNode(0);
        dummy.next=head;
        ListNode tempDummy=dummy;
        ListNode cur=head;
        //allow node => null
        while(cur!=null && cur.next!=null){
            tempDummy.next=cur.next;//swap begin
            cur.next=cur.next.next;
            tempDummy.next.next=cur;//swap completed
            //move both nodes to next adjacent pairs
            tempDummy=cur;
            cur=cur.next;
        }
        return dummy.next;
    }
}