[面试真题] 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.

解法：游标指针从头节点向后移动，当指向尾节点时，得到链表长度len，同时将链表头尾相连，接着游标再向后移动 k % len 步得到结果链表的尾节点。

/**
 * 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(head){
            int len = 1;
            ListNode *p = head;
            while(p->next){
            p = p->next;
            len++;
            }
            p->next = head;
            k %= len;
            int step = len - k;
            while(step>0){
                p = p->next;
                step--;
            }
            head = p->next;
            p->next = NULL;
        }
        return head;
    }
};

Run Status: Accepted!
Program Runtime: 56 milli secs

Progress: 229/229 test cases passed.