【每日一题Day287】LC24 两两交换链表中的节点 | 模拟 递归

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode swapPairs(ListNode head) {
        ListNode dummyNode = new ListNode(-1,head);
        ListNode pre = dummyNode;
        ListNode cur = pre.next;
        while(pre != null && cur !=null && cur.next != null){
            ListNode tmp = cur.next.next;
            pre.next = cur.next;
            cur.next.next = cur;
            cur.next = tmp;
            pre = cur;
            cur = cur.next;
        }
        return dummyNode.next; 
    }
}

2022/09/21
class Solution {
    public ListNode swapPairs(ListNode head) {
        ListNode dummyHead = new ListNode(0,head);
        ListNode node = dummyHead;
        while (node.next != null && node.next.next != null){
            ListNode nn = node.next.next;
            node.next.next = nn.next;
            nn.next = node.next;
            node.next = nn;
            node = node.next.next;
        }
        return dummyHead.next;
    }
}

class Solution {
    public ListNode swapPairs(ListNode head) {
        if (head == null || head.next == null) {
            return head;
        }
        ListNode newHead = head.next;
        head.next = swapPairs(newHead.next);
        newHead.next = head;
        return newHead;
    }
}
作者：LeetCode-Solution
链接：https://leetcode-cn.com/problems/swap-nodes-in-pairs/solution/liang-liang-jiao-huan-lian-biao-zhong-de-jie-di-91/
来源：力扣（LeetCode）
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。