題目描述

鏈接：https://leetcode-cn.com/problems/rotate-list/
給你一個(gè)鏈表的頭節(jié)點(diǎn) head ，旋轉(zhuǎn)鏈表，將鏈表每個(gè)節(jié)點(diǎn)向右移動(dòng) k 個(gè)位置。

示例

輸入：head = [1,2,3,4,5], k = 2
輸出：[4,5,1,2,3]

代碼

    public ListNode rotateRight(ListNode head, int k) {
        if (head == null || k <= 0) {
            return head;
        }

        int length = 1; // 鏈表長(zhǎng)度
        ListNode tempHead = head;
        ListNode lastNode = null; // 鏈表最后一個(gè)節(jié)點(diǎn)
        // 計(jì)算鏈表長(zhǎng)度
        while (tempHead.next != null) {
            length ++;
            tempHead = tempHead.next;
        }
        lastNode = tempHead;

        // 如果k大于鏈表長(zhǎng)度，則取余數(shù)
        if (k >= length) {
            k = k % length;
        }

        // 如果k = 0，表示不用旋轉(zhuǎn)，則直接返回head
        if (k == 0) {
            return head;
        }

        // 找到旋轉(zhuǎn)后鏈表的頭部位置
        tempHead = head;
        for (int i = 0; i < length - k - 1; i++) {
            tempHead = tempHead.next;
        }

        ListNode newHead = tempHead.next;
        tempHead.next = null; // 斷開指向頭部的指針
        lastNode.next = head; // 鏈表最后一個(gè)元素執(zhí)行原始的頭節(jié)點(diǎn)
        return newHead;
    }