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Leetcode-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.
Have you met this question in a real interview?
Solution:
1 /** 2 * Definition for singly-linked list. 3 * public class ListNode { 4 * int val; 5 * ListNode next; 6 * ListNode(int x) { 7 * val = x; 8 * next = null; 9 * }10 * }11 */12 public class Solution {13 public ListNode swapPairs(ListNode head) {14 if (head==null || head.next==null) return head;15 ListNode preHead = new ListNode(0);16 preHead.next = head;17 ListNode pre = preHead;18 ListNode cur = head;19 20 while (cur!=null && cur.next!=null){21 ListNode temp = cur.next.next;22 pre.next = cur.next;23 cur.next.next = cur;24 cur.next = temp;25 pre=cur;26 cur = cur.next;27 }28 29 return preHead.next;30 }31 }
Leetcode-Swap Nodes in Pairs
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