[LintCode/LeetCode] Rotate Array

Problem

Given an array, rotate the array to the right by k 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]

Solution

public class Solution {
    /**
     * @param nums: an array
     * @param k: an integer
     * @return: rotate the array to the right by k steps
     */
    public int[] rotate(int[] nums, int k) {
        // Write your code here
        k = k % nums.length; //point 1
        revert(nums, 0, nums.length-k-1); //point 2
        revert(nums, nums.length-k, nums.length-1);
        revert(nums, 0, nums.length-1);
        return nums;
        
    }
    private void revert(int[] nums, int start, int end) {
        while (start < end) {
            int temp = nums[start];
            nums[start] = nums[end];
            nums[end] = temp;
            start++;
            end--;
        }
    }
}