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leetcode--Rotate List

2024-07-07 03:42:25   220人阅读

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

For example:
Given 1->2->3->4->5->NULL and k = 2,
return 4->5->1->2->3->NULL.

?
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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
 
public class Solution {
    /**
     * The problem is to find the n-th nodes from end of the list.<br>
     * Notice that the number n may be greater than the length of the list.<br>
     * If this happen, we let n = n % length of the list.<br>
     *
     * @param head --The head node of the input list
     * @param n --An integer.
     * @return head of the rotated list.
     * @author Averill Zheng
     * @version 2014-06-03
     * @since JDK 1.7
     */
    public ListNode rotateRight(ListNode head, int n) {
        ListNode newHead = null;
        //calculate the length of the list
        if(head != null){
            int length = 0;
            ListNode currentNode = head;
            while(currentNode != null){
                ++length;
                currentNode = currentNode.next;
            }
            n = (n < length) ?  n :  n % length;
            if(n > 0){
                currentNode = head;
                ListNode tail = null;
                for(int i = 0; i < length - n; ++i){
                    tail = currentNode;
                    currentNode = currentNode.next;
                }
                newHead = currentNode;
                while(currentNode.next != null)
                    currentNode = currentNode.next;        
                currentNode.next = head;
                tail.next = null;
            }
            else
                newHead = head;
        }
        return newHead;
    }
}

　　


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