LeetCode: 189. Rotate Array

题目描述

Given an array, rotate the array to the right by k steps, where k is non-negative.

Example 1:

Input: [1,2,3,4,5,6,7] and k = 3
Output: [5,6,7,1,2,3,4]
Explanation:
rotate 1 steps to the right: [7,1,2,3,4,5,6]
rotate 2 steps to the right: [6,7,1,2,3,4,5]
rotate 3 steps to the right: [5,6,7,1,2,3,4]

Example 2:

Input: [-1,-100,3,99] and k = 2
Output: [3,99,-1,-100]
Explanation: 
rotate 1 steps to the right: [99,-1,-100,3]
rotate 2 steps to the right: [3,99,-1,-100]

Note:

• Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
• Could you do it in-place with O(1) extra space?

解题思路

递归求解，一次移动一位。

AC 代码

class Solution {
public:
    void rotate(vector<int>& nums, int k) {
        if(k == 0 || nums.empty()) return;

        // 向右边移动一位
        int lastNum = nums.back(); 
        for(int i = nums.size()-1; i > 0; --i)
        {
            nums[i] = nums[i-1];
        }
        nums[0] = lastNum;

        // 继续移动 k-1 位
        rotate(nums, k-1);
    }
};