170. 旋转链表

给定一个链表，旋转链表，使得每个节点向右移动k个位置，其中k是一个非负数

您在真实的面试中是否遇到过这个题？

Yes

样例

给出链表1->2->3->4->5->null和k=2

返回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:
    /*
     * @param head: the List
     * @param k: rotate to the right k places
     * @return: the list after rotation
     */
    ListNode * rotateRight(ListNode * head, int k) {
        // write your code here
         if (!head) return NULL;
        int n = 1;
        ListNode *cur = head;
        while (cur->next) {
            ++n;
            cur = cur->next;
        }
        cur->next = head;
        int m = n - k % n;
        for (int i = 0; i < m; ++i) {
            cur = cur->next;
        }
        ListNode *newhead = cur->next;
        cur->next = NULL;
        return newhead;

    }
};