using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        int[] firstArray = {2,4,6,8,10};

        int[] secondArray= {1,2,3,5,6,8,9};

        var result = ArrayIntersection(firstArray, secondArray);

        foreach(int element in result)

        {

            Console.WriteLine(element);

        }       

    }

    public static int[] ArrayIntersection(int[] firstArray, int[] secondArray)

    {

        // the assumption is that array are sorted. If not, first sort the array by calling Array.Sort(arrayName)

        // Array.Sort is an inbuilt function

        // Array.Sort(firstArray);

        int firstArrayLength = firstArray.Length;

        int secondArrayLength = secondArray.Length;

        // create a resultArray and lets set the size as the sum of first and second array length

        // result array should be either equal to sum of first and second array or less than that if there are duplicates between arrays

        // the way we can create a new array by reserving the size is

        // int[] newArray = new int[size];  // eg if we want to create an array of size 6

        // int[] newArray = new int[6];

        // if we want to set the first element value to say 120

        // newArray[0] = 120;

        // newArray[1] = 200;

        int[] resultArray = new int[firstArrayLength + secondArrayLength];

        // we will use i for firstArray position. 

        int i = 0;

        // we will use j as pos for secondArray.

        int j = 0;

        // we will use k as pos for result array

        int k = 0;

        // we run the while loop until i < firstArrayLength or j < secondArrayLength

        // || is the sign for "OR" condition in C#  

        // so if we reach at the end of both arrays, than while loop ends

        while(i < firstArrayLength || j < secondArrayLength)

        {

            // if we have reached at the end of the firstArray

            // we know we just can copy the second array

            if(i >= firstArrayLength)

            {

                resultArray[k] = secondArray[j];

                j++;

            }

            // if we have reached at the end of the secondArray

            // we know we just can copy the second array

            else if(j >= secondArrayLength)

            {

                resultArray[k] = firstArray[i];

                i++;

            }

            // if first Array value at pos i is less than second Array value at pos j

            // we are going to copy firstArray ith value to resultArray and increment i and k

            else if(firstArray[i] < secondArray[j])

            {

                resultArray[k] = firstArray[i];

                i++;

            }

            else if(firstArray[i] > secondArray[j])

            {

                resultArray[k] = secondArray[j];

                j++;

            }

            // if first two conditions are not met, that means both ith and jth pos element values are same

            // which means we copy either one and move both positions i and j

            else

            {

                resultArray[k] = firstArray[i];

                i++;

                j++;

            }

            // after each loop, increment k otherwise we would just be overriding the same value

            k++;                

        }

        return resultArray;

    }

}