[LeetCode]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?

这道题是要求将数组中的元素循环右移k位。

如果k<= n,通过观察可以发现，通过三步可以将要求完成：
①将数组前n-k位反转
②将数组后k位反转
③将数组整体反转

但是，如果k>n，则需要多走一步，就是k=k%n。
代码如下：

class Solution {
public:
    void swap(int& a,int& b){
        int temp=a;
        a=b;
        b=temp;
    }
    void reverse(int nums[],int begin,int end){
        for(int i=begin,j=end;i<j;i++,j--){
            swap(nums[i],nums[j]);
        }
    }
    void rotate(int nums[], int n, int k) {
        int step=k%n;
        reverse(nums,0,n-step-1);
        reverse(nums,n-step,n-1);
        reverse(nums,0,n-1);
    }
};