LeetCode_189. Rotate Array

189. Rotate Array

Easy

Given an array, rotate the array to the right by k steps, where k is non-negative.

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:

• Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
• Could you do it in-place with O(1) extra space?

package leetcode.easy;

public class RotateArray {
	private static void print_arr(int[] nums) {
		for (int num : nums) {
			System.out.print(num + " ");
		}
		System.out.println();
	}

	public void rotate1(int[] nums, int k) {
		int temp, previous;
		for (int i = 0; i < k; i++) {
			previous = nums[nums.length - 1];
			for (int j = 0; j < nums.length; j++) {
				temp = nums[j];
				nums[j] = previous;
				previous = temp;
			}
		}
	}

	public void rotate2(int[] nums, int k) {
		int[] a = new int[nums.length];
		for (int i = 0; i < nums.length; i++) {
			a[(i + k) % nums.length] = nums[i];
		}
		for (int i = 0; i < nums.length; i++) {
			nums[i] = a[i];
		}
	}

	public void rotate3(int[] nums, int k) {
		k = k % nums.length;
		int count = 0;
		for (int start = 0; count < nums.length; start++) {
			int current = start;
			int prev = nums[start];
			do {
				int next = (current + k) % nums.length;
				int temp = nums[next];
				nums[next] = prev;
				prev = temp;
				current = next;
				count++;
			} while (start != current);
		}
	}

	public void rotate4(int[] nums, int k) {
		k %= nums.length;
		reverse(nums, 0, nums.length - 1);
		reverse(nums, 0, k - 1);
		reverse(nums, k, nums.length - 1);
	}

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

	@org.junit.Test
	public void test1() {
		int[] nums1 = { 1, 2, 3, 4, 5, 6, 7 };
		int k1 = 3;
		int[] nums2 = { -1, -100, 3, 99 };
		int k2 = 2;
		print_arr(nums1);
		rotate1(nums1, k1);
		print_arr(nums1);

		print_arr(nums2);
		rotate1(nums2, k2);
		print_arr(nums2);
	}

	@org.junit.Test
	public void test2() {
		int[] nums1 = { 1, 2, 3, 4, 5, 6, 7 };
		int k1 = 3;
		int[] nums2 = { -1, -100, 3, 99 };
		int k2 = 2;
		print_arr(nums1);
		rotate2(nums1, k1);
		print_arr(nums1);

		print_arr(nums2);
		rotate2(nums2, k2);
		print_arr(nums2);
	}

	@org.junit.Test
	public void test3() {
		int[] nums1 = { 1, 2, 3, 4, 5, 6, 7 };
		int k1 = 3;
		int[] nums2 = { -1, -100, 3, 99 };
		int k2 = 2;
		print_arr(nums1);
		rotate3(nums1, k1);
		print_arr(nums1);

		print_arr(nums2);
		rotate3(nums2, k2);
		print_arr(nums2);
	}

	@org.junit.Test
	public void test4() {
		int[] nums1 = { 1, 2, 3, 4, 5, 6, 7 };
		int k1 = 3;
		int[] nums2 = { -1, -100, 3, 99 };
		int k2 = 2;
		print_arr(nums1);
		rotate4(nums1, k1);
		print_arr(nums1);

		print_arr(nums2);
		rotate4(nums2, k2);
		print_arr(nums2);
	}
}