leetcode206 反转链表两种做法（循环，递归）

2024-10-07 05:26:09

反转链表 leetcode206

方法1 循环

public ListNode reverseList(ListNode head) {

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

            return head;

        }

        ListNode now = head;

        while (now.next != null) {

            ListNode temp = now.next;

            now.next = now.next.next;

            temp.next = head;

            head = temp;

        }

        return head;

    }

方法2 递归

public ListNode reverseList2(ListNode head) {

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

            return head;

        }

        ListNode newHead = reverseList2(head.next);

        ListNode now =newHead;

        while (now.next != null) {

            now = now.next;

        }

        now.next = head;

        head.next = null;

        return newHead;

    }

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