旋转链表

/**
 * 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) return NULL;
        if(k == 0) return head;
        
        ListNode* p = head;
        int len = 1;
        //首先构建环形链表
        while(p->next){
           // cout << p->val << ",";
            p = p->next;
            len++;
        } 
        //len ++;
        cout << "len:" << len << endl;
        p->next = head;  //当使用p = head的时候没有形成环形链表,p为最后一个结点指向的空指针next.
        int i = 0;
        ListNode* pk = head;
        int index = 0;
        //其次对链表进行位移
        while(index < len-k%len-1){
            cout << pk->val << ",";
            pk = pk->next;
            index++;
        }        
        head = pk->next;
        //相应位置进行断开
        pk->next = NULL;
        //pk->next = NULL;
      /*  ListNode* tp = head;
        while(tp){
            cout << tp->val << "->";
            tp = tp->next;
        }*/
        return head;        
    }
};