LeetCode(67)-Rotate Array

题目：

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.

思路：

• 题意：要求对给定长度的整形数组n进行平移，给定k，就平移3个位置（循环）
• 要求是在o（1）的空间，不能考虑数组的复制了，根据算法，这个平移转化为逆序。reverse（nums，0，n-k-1），reverse（nums，n-k，n-1），reverse（nums，0，n-1）等价，写一个reverse的函数。

代码：

public class Solution {
    public void reverse(int[] nums,int start,int end){
            while(start < end){
                int tmp = nums[start];
                nums[start] = nums[end];
                nums[end] = tmp;
                start++;
                end--;
            }
        }
    public void rotate(int[] nums, int k) {
        if(nums.length == 0){
            return;
        }
        int n = nums.length;
        k = k%n;
        reverse(nums,0,n-k-1);
        reverse(nums,n-k,n-1);
        reverse(nums,0,n-1);
    }
}