LeetCode92(2021.3.18)

LC92. 反转链表 II

class Solution {
    private void reverseLinkedList(ListNode head) {
        ListNode pre = null;
        ListNode cur = head;
        while (cur != null) {
            ListNode next = cur.next;
            cur.next = pre;
            pre = cur;
            cur = next;
        }
    }

    public ListNode reverseBetween(ListNode head, int left, int right) {
        ListNode dummyNode = new ListNode(-1);
        dummyNode.next = head;
        ListNode pre = dummyNode;
        for (int i = 0; i < left - 1; i++) {
            pre = pre.next;
        }
        ListNode rightNode = pre;
        for (int i = 0; i < right - left + 1; i++) {
            rightNode = rightNode.next;
        }

        //截取链表
        ListNode leftNode = pre.next;
        ListNode curr = rightNode.next;
        pre.next = null;
        rightNode.next = null;

        //反转链表
        reverseLinkedList(leftNode);

        pre.next = rightNode;
        leftNode.next = curr;
        return dummyNode.next;
    }
}