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  • 24. 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.

    /**
     * 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 dummy = new ListNode(0);
            dummy.next = head;
            ListNode cur = dummy;
            while(cur != null && cur.next != null && cur.next.next != null){
                ListNode slow = cur.next;
                ListNode fast =  cur.next.next;
                slow.next = fast.next;
                cur.next = fast;
                cur.next.next = slow;
                cur = slow;
            }
            return dummy.next;
        }
    }
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  • 原文地址:https://www.cnblogs.com/joannacode/p/6012364.html
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