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  • 61. Rotate List

    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

    time: O(n), space: O(1)

    /**
     * Definition for singly-linked list.
     * public class ListNode {
     *     int val;
     *     ListNode next;
     *     ListNode(int x) { val = x; }
     * }
     */
    class Solution {
        public ListNode rotateRight(ListNode head, int k) {
            if(head == null) {
                return head;
            }
            int len = 0;
            ListNode cur = head;
            while(cur != null) {
                cur = cur.next;
                len++;
            }
            k = k % len;
            
            ListNode p1 = head, p2 = head;
            for(int i = 0; i < k; i++) {
                p1 = p1.next;
            }
            while(p1.next != null) {
                p1 = p1.next;
                p2 = p2.next;
            }
            p1.next = head;
            head = p2.next;
            p2.next = null;
            
            return head;
        }
    }
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  • 原文地址:https://www.cnblogs.com/fatttcat/p/10184940.html
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