[LeetCode]Rotate List

题目描述:(链接)

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.

解题思路:

注意k会大于链表长度： k % length.

/**
 * 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 || k == 0) return head;
        
        int length = 1;
        ListNode *cur = head;
        for (; cur->next != nullptr ; cur = cur->next) {
            ++length;
        }
        k = length - k % length;
        
        cur->next = head;
        for (int i =0; i < k; i++) {
            cur = cur->next;
        }
        
        head = cur->next;
        cur->next = nullptr;
        
        return head;
    }
};