189. Rotate Array

Posted 2020-08-08 whl-hl

1. 问题描述

189. Rotate Array
Rotate an array of n elements to the right by k steps.
For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].
Note:
Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
Hint:
Could you do it in-place with O(1) extra space?
Related problem: Reverse Words in a String II
Tags: Array
Similar Problems: (M) Rotate List (M) Reverse Words in a String II

2. 解题思路

3. 代码

#include <algorithm>
class Solution {
public:
    void rotate_1(vector<int>& nums, int k) 
    {
        int vSize = nums.size();
        k = k % vSize;
        for (int i=0; i<vSize/2; i++)
        {
            int t = nums[i];
            nums[i] = nums[vSize-1-i];
            nums[vSize-1-i] = t;
        }

        for (int i=0; i<k/2; i++)
        {
            int t = nums[i];
            nums[i] = nums[k-1-i];
            nums[k-1-i] = t;
        }

        for (int i=k; i<k + (vSize-k)/2; i++)
        {
            int t = nums[i];
            nums[i] = nums[vSize-1-i+k];
            nums[vSize-1-i+k] = t;
        }
    }

    void rotate_2(vector<int>& nums, int k)//使用reverse()函数需引入#include <algorithm>
    {
        k = k % nums.size();
        reverse(nums.begin(), nums.end());
        reverse(nums.begin(), nums.begin()+k);
        reverse(nums.begin()+k, nums.end());
    }
};

 

4. 反思