LeetCode-Rotate List

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.

记住是向右移。。

/**
 * 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) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if(k==0)return head;
        if(head==NULL)return NULL;
        ListNode* tail,*ret,*ptr;
        tail=head;
        while(tail->next!=NULL)tail=tail->next;
        if(tail==head)return head;
        for(int i=0;i<k;i++){
            ptr=head;
            while(ptr->next!=tail)ptr=ptr->next;
            tail->next=head;
            head=tail;
            ptr->next=NULL;
            tail=ptr;
        }
        return head;
    }
};