using Microsoft.VisualStudio.TestTools.UnitTesting;

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace Algorithms.Problem.Arrays

{

[TestClass]

public class RotateArray

{

/// <summary>

/// Rotate array for k times.

/// </summary>

/// <param name="array">Given array for rotation.</param>

/// <param name="k">Number of times to rotate.</param>

public void ArrayRotation(int[] array, int k)

{

/// For ex:

/// array = 1,2,3,4,5,6

/// k = 3

/// result = 4,5,6,1,2,3

/// space: o(1) and time: o(n)

/// step1: Divide into 2 - first part: 1,2,3 second part: 4,5,6

/// step2: reverse 1st part 3,2,1

/// step3: reverse 2nd part: 6,5,4 {3,2,1,6,5,4}

/// step2: reverse the whole array : {4,5,6,1,2,3}

int length = array.Length;

int firstPart = array.Length - k - 1;

int secondPart = firstPart + 1;

reverseArray(array, 0, firstPart);

reverseArray(array, secondPart, array.Length - 1);

reverseArray(array, 0, array.Length -1);

}

public void reverseArray(int[] array, int startIndex, int endIndex)

{

while(startIndex < endIndex)

{

int temp = array[startIndex];

array[startIndex] = array[endIndex];

array[endIndex] = temp;

startIndex = startIndex + 1;

endIndex = endIndex - 1;

}

}

[TestMethod]

public void TestRotateArray()

{

int[] array = { 1, 2, 3, 4, 5, 6 };

int k = 3;

this.ArrayRotation(array, k);

int[] expectedArray = { 4,5,6,1,2,3 };

for(int i = 0; i< expectedArray.Length - 1; i++)

{

Assert.AreEqual(array[i], expectedArray[i], "The expected value is invalid!");

}

}

}

}