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Java-based LeetCode algorithm problem solutions, regularly updated

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package g0001_0100.s0061_rotate_list;

// #Medium #Two_Pointers #Linked_List #Programming_Skills_II_Day_16 #Udemy_Linked_List
// #2023_08_11_Time_0_ms_(100.00%)_Space_41.1_MB_(94.89%)

import com_github_leetcode.ListNode;

/*
 * 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; }
 * }
 */
/**
 * 61 - Rotate List\.
 *
 * Medium
 *
 * Given the `head` of a linked list, rotate the list to the right by `k` places.
 *
 * **Example 1:**
 *
 * ![](https://assets.leetcode.com/uploads/2020/11/13/rotate1.jpg)
 *
 * **Input:** head = [1,2,3,4,5], k = 2
 *
 * **Output:** [4,5,1,2,3] 
 *
 * **Example 2:**
 *
 * ![](https://assets.leetcode.com/uploads/2020/11/13/roate2.jpg)
 *
 * **Input:** head = [0,1,2], k = 4
 *
 * **Output:** [2,0,1] 
 *
 * **Constraints:**
 *
 * *   The number of nodes in the list is in the range `[0, 500]`.
 * *   `-100 <= Node.val <= 100`
 * *   0 <= k <= 2 * 10⁹
**/
public class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if (head == null || k == 0) {
            return head;
        }
        ListNode tail = head;
        // find the count and let tail points to last node
        int count = 1;
        while (tail != null && tail.next != null) {
            count++;
            tail = tail.next;
        }
        // calculate number of times to rotate by count modulas
        int times = k % count;
        if (times == 0) {
            return head;
        }
        ListNode temp = head;
        // iterate and go to the K+1 th node from the end or count - K - 1 node from
        // start
        for (int i = 1; i <= count - times - 1 && temp != null; i++) {
            temp = temp.next;
        }
        ListNode newHead = null;
        if (temp != null && tail != null) {
            newHead = temp.next;
            temp.next = null;
            tail.next = head;
        }
        return newHead;
    }
}