61. Rotate List （旋转链表）

题目链接：https://leetcode.com/problems/rotate-list/description/

题目大意：给一个链表，将其旋转K次得到最终链表

题解：显然是个要求循环节的问题，求好后先将需要翻转的那部分加入新的链表中，再将剩余（即头结点）后的加入，需要注意最终的终止条件是NULL

= =、最近要准备面试的东西，还是得多写点题

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    int calcu(ListNode* head)
    {
        int n = 0 ;
        while(head)
        {
            n++;
            head = head->next;
        }
        return n;
    }
    ListNode* rotateRight(ListNode* head, int k) {
        ListNode *p = head ;
        ListNode *newlist = new ListNode(0);
        ListNode *list = newlist;
        int cnt = calcu(head);
        if(cnt==0) return NULL;
        if(cnt==1) return head;
        k = k%cnt;
        for(int i = 0 ; i < cnt-k ; i++) 
        {
            p = p->next;
        }
        for(int i = 0 ; i < k ; i++) 
        {
            list->next = p ;
            cout<next->val<<" ";
            list = list->next;
            p = p->next;
        }
        cout<next = head;
            cout<next->val<<" ";
            head = head->next;
            list = list->next;
        }
        cout<next = NULL;
        newlist = newlist->next;
        return newlist;
    }
};