algorithms/cpp/rotateList/rotateList.cpp

// Source : https://oj.leetcode.com/problems/rotate-list/
// Author : Hao Chen
// Date   : 2014-06-20

/********************************************************************************** 
* 
* 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.
*               
**********************************************************************************/

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *rotateRight(ListNode *head, int k) {
        if (!head || k<=0){
            return head;
        }
        
        //find the length of List
        int len=1;
        ListNode *p=head;
        while( p->next != NULL ){
            p = p->next;
            len++;
        }
        //connect the tail to head
        p->next = head;
        //find the left place (take care the case - k > len)
        k = len - k % len;
        
        //find the place
        for(int i=0; i<k; i++){
            p = p->next;
        }
        
        //break the list
        head = p->next;
        p->next = NULL;
        
        return head;
        
    }
};