_189.java

package com.fishercoder.solutions;

import java.util.ArrayList;
import java.util.List;

import static com.fishercoder.solutions._189.Solution2.rotate_naive;

/**
 * 189. 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].
 * */

public class _189 {

    public static class Solution1 {
        public void rotate(int[] nums, int k) {
            int len = nums.length;
            int[] tmp = new int[len];
            for (int i = 0; i < len; i++) {
                tmp[(i + k) % len] = nums[i];
            }
            for (int i = 0; i < len; i++) {
                nums[i] = tmp[i];
            }
        }
    }

    public static class Solution2 {
        /**
         * My original idea and got AC'ed.
         * One thing to notice is that when k > nums.length, we'll continue to rotate_naive the array, it just becomes k -= nums.length
         */
        public static void rotate_naive(int[] nums, int k) {
            if (k == 0 || k == nums.length) {
                return;
            }
            if (k > nums.length) {
                k -= nums.length;
            }
            List<Integer> tmp = new ArrayList();
            int i = 0;
            if (nums.length - k >= 0) {
                i = nums.length - k;
                for (; i < nums.length; i++) {
                    tmp.add(nums[i]);
                }
            } else {
                i = nums.length - 1;
                for (; i >= 0; i--) {
                    tmp.add(nums[i]);
                }

            }
            for (i = 0; i < nums.length - k; i++) {
                tmp.add(nums[i]);
            }
            for (i = 0; i < tmp.size(); i++) {
                nums[i] = tmp.get(i);
            }
        }
    }

    public static void main(String... strings) {
//        int k = 1;
//        int[] nums = new int[]{1,2,3};
//        int[] nums = new int[]{1};
//        int[] nums = new int[]{1,2};

//        int k = 3;
//        int[] nums = new int[]{1,2};

//        int k = 2;
//        int[] nums = new int[]{1,2};

        int k = 4;
        int[] nums = new int[]{1, 2, 3};

//        int k = 2;
//        int[] nums = new int[]{-1};
        rotate_naive(nums, k);
    }

}