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leetcode 61. rotate list

admin 11月 13, 2020 0

61. Rotate List

Difficulty: Medium

Given a linked list, rotate the list to the right by k places, where k is non-negative.

Example 1:

Input: 1->2->3->4->5->NULL, k = 2
Output: 4->5->1->2->3->NULL
Explanation:
rotate 1 steps to the right: 5->1->2->3->4->NULL
rotate 2 steps to the right: 4->5->1->2->3->NULL

Example 2:

Input: 0->1->2->NULL, k = 4
Output: 2->0->1->NULL
Explanation:
rotate 1 steps to the right: 2->0->1->NULL
rotate 2 steps to the right: 1->2->0->NULL
rotate 3 steps to the right: 0->1->2->NULL
rotate 4 steps to the right: 2->0->1->NULL

Solution

Language: Java


 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class  {
    public ListNode rotateRight(ListNode head, int k) {
        if (head == null || head.next == null || k == 0) {
            return head;
        }
        int count = 1;
        ListNode cur = head;
        while (cur.next != null) {
            count++;
            cur = cur.next;
        }
        cur.next = head;
        k %= count;
        for (int i = 0; i < (count - k - 1); i++) {
            head = head.next;
        }
        ListNode next = head.next;
        head.next = null;
        return next;
    }
}