Rotate Array

Given an array, rotate the array to the right byk_steps, where _k is non-negative.

Example

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

三步翻转法

abcd | efg => 两段分别反序

dcba | gfe => 整体反序

efgabcd

Code

class Solution {
    public void rotate(int[] nums, int k) {
        // (i + k)%nums.length
        k %= nums.length;
        reverse(nums, 0, nums.length - 1);
        reverse(nums, 0, k - 1);
        reverse(nums, k, nums.length - 1);
    }

    private void reverse(int[] nums, int start, int end) {
        while (start < end) {
            int temp = nums[start];
            nums[start++] = nums[end];
            nums[end--] = temp;
        }
    }
}