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.

为了方便，使用了哨兵节点。

java：

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode rotateRight(ListNode head, int n) {
        if(head==null||head.next==null||n==0)
            return head;
        int cnt=0;
        ListNode p=head;
        while(p!=null){
            cnt++;
            p=p.next;
        }
        if(n==cnt)
            return head;
        n=n%cnt;
        if(0==n)
            return head;
        ListNode h = new ListNode(-1);
        h.next=head;
        ListNode q=h;
        int step=0;
        while(step<n){
            step++;
            q=q.next;
        }
        p=h;
        while(q.next!=null){
            q=q.next;
            p=p.next;
        }
        q.next=h.next;
        h.next=p.next;
        p.next=null;
        
        return h.next;
        
    }
}

c++：

/**
 * 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||!head->next||0==k){
            return head;
        }
        ListNode *p=head;
        int N=0;
        while(p){
            N++;
            p=p->next;
        }
        if(k==N)
            return head;
        k=k%N;
        if(k==0)
            return head;
        ListNode *h = (ListNode *)malloc(sizeof(ListNode));
        h->next=head;
        
        ListNode*q=h;
        int cnt=0;
        while(cnt<k){
            cnt++;
            q=q->next;
        }
        p=h;
        while(q->next){
            q=q->next;
            p=p->next;
        }
        q->next=h->next;
        h->next=p->next;
        p->next=NULL;
        
        ListNode *s =h->next;
        free(h);
        return s;
        
    }
};