Rotate Array

This is a classical problem. The best solution is of time cost and space cost . In this problem we rotate the array to the right but we can also rotate an array to the left using the same method with just a little modification.

The method concerns about reverse partial or whole array three times. Note that your code must handle cases that k is greater than the array's length. Sample code:

public class RotateArray {
    private void reverse(int[] nums, int i, int j) {
        while (i < j) {
            int t = nums[i];
            nums[i] = nums[j];
            nums[j] = t;
    public void rotate(int[] nums, int k) {
        k %= nums.length;
        if (k == 0) return;

        reverse(nums, 0, nums.length - k - 1);
        reverse(nums, nums.length - k, nums.length - 1);
        reverse(nums, 0, nums.length - 1);