LeetCode: 24. Swap Nodes in Pairs

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24. Swap Nodes in Pairs

LeetCode - Swap Nodes in Pairs

Given a linked list, swap every two adjacent nodes and return its head.

You may not modify the values in the list’s nodes, only nodes itself may be changed.

Example:

Given 1->2->3->4, you should return the list as 2->1->4->3.

思考题

尝试使用递归来实现一下。

参考资料

两两交换链表中的节点 - 两两交换链表中的节点 - 力扣（LeetCode）

Given a linked list, swap every two adjacent nodes and return its head.

You may not modify the values in the list’s nodes, only nodes itself may be changed.

Example:

Given 1->2->3->4, you should return the list as 2->1->4->3.

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/**
 * Runtime: 0 ms, faster than 100.00% of Java online submissions for Swap Nodes in Pairs.
 * Memory Usage: 37.3 MB, less than 5.50% of Java online submissions for Swap Nodes in Pairs.
 */
public ListNode swapPairs(ListNode head) {
    if (Objects.isNull(head) || Objects.isNull(head.next)) {
        return head;
    }
    ListNode result = head.next;
    ListNode prevNode = new ListNode(0);
    prevNode.next = head;
    while (Objects.nonNull(head) && Objects.nonNull(head.next)) {
        ListNode second = head.next;
        head.next = second.next;
        second.next = head;
        prevNode.next = second;
        prevNode = head;
        head = head.next;
    }

    return result;
}