开始刷leetcode day29：Swap Nodes in Pairs

最新推荐文章于 2021-11-23 16:05:07 发布

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本文介绍了一种算法，该算法能在常数空间内交换给定链表中的每两个相邻节点，通过改变节点指针而非节点值实现。例如将1->2->3->4变换为2->1->4->3。提供了Java实现代码。

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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.

Java:

/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
public class Solution {
public ListNode swapPairs(ListNode head) {
if(head == null || head.next == null) return head;

ListNode newNode = head.next;
head.next = head.next.next;
newNode.next = head;
head = head.next;
ListNode newHead = newNode;
newNode = newNode.next;

while(head!= null && head.next != null)
{
newNode.next = head.next;
head.next = head.next.next;
newNode.next.next = head;
newNode = head;
head = head.next;
}

return newHead;

}
}