using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        //Console.WriteLine("Hello World");

        int[] InputArray = new int[] {5,8,10,20,11,7};

        //int[] InputArray = new int[] {6,9,11,21,12,8}; //6 9 12 11 8 21

        int[] FinalArray = ShiftEvenIntegersToEvenIndexAndOddIntegersToOddIndex(InputArray);

        for(int i=0; i<FinalArray.Length; i++)

        {

            Console.Write(FinalArray[i].ToString()+ "\t");

        }

    }

    /// <summary>

/// Take an input of integers , shift all even integers to even index and odd integers to odd index

/// Consider 0 as even index

/// Example if input in 5,8,10,20,11,7

/// Out put is 8,5,10,11,20,7

/// </summary>

/// <param name="integers">array of integers</param>

/// <returns>shifted integers</returns>

    public static int[] ShiftEvenIntegersToEvenIndexAndOddIntegersToOddIndex(int[] integers)

    {

        int[] OutputArray = new int[integers.Length];

        List<int> lstEvenNumbers = new List<int>();      

        List<int> lstOddNumbers = new List<int>();       

        foreach(int i in integers)

        {

           if(i%2 == 0)

             lstEvenNumbers.Add(i);

            else

             lstOddNumbers.Add(i);

        }

        int[] EvenNumbersArray = lstEvenNumbers.ToArray();

        int[] OddNumbersArray = lstOddNumbers.ToArray();

        int j = 0; int k=0;

        for(int i=0 ; i<integers.Length; i++)

        {

            if(i==0 || i%2==0)

            {

                OutputArray[i] = EvenNumbersArray[j];

                j++;

            }

            else

            {

                OutputArray[i] = OddNumbersArray[k];

                k++;

            }

        }

        return OutputArray;

    }

}

​

​