algorithm/Week_01/id_134/LeetCode_24_134.java at master · feixiangcode/algorithm · GitHub

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//https://leetcode.com/problems/swap-nodes-in-pairs/

/**

* Definition for singly-linked list.

* public class ListNode {

* int val;

* ListNode next;

* ListNode(int x) { val = x; }

* }

class Solution {

public ListNode swapPairs(ListNode head) {

if (head == null || head.next == null)

return head;

ListNode prev = head, cur = head.next, after = null;

ListNode sentinel = new ListNode(0), ret = head.next;

sentinel.next = head;

while (prev != null && cur != null ) {

after = cur.next;

prev.next = cur.next;

cur.next = prev;

sentinel.next = cur;

sentinel = sentinel.next.next;

prev = after;

if (after != null)

cur = after.next;

}

return ret;

}

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