leetcode 61 Rotate List
z
 2018-05-05 21:36:26  
  1. Rotate List

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

Example 1:

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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:

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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
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/**
 * 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) {
        int length = 1;
        ListNode tag = head;
        ListNode tail = head;
        if (head == null){
            return head;
        }
        while(tail.next != null){
            tail = tail.next;
            length ++;
        }
        k = (length - (k % length)) - 1;
        tag = head;
        int i = 0;
        while(i < k){
            tag = tag.next;
            i++;
        }
        ListNode t = tag.next;
        if(t == null){
            return head;
        }
        tag.next = null;
        tail.next = head;
        return t;
    }
}

python

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