using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        var a = new int[] { int.MinValue, 4, 1, 3, 2, 16, 9, 10, 14, 8, 7};

        BuildHeap(ref a);

        Console.WriteLine(string.Join(",", a));

    }

    private static void BuildHeap(ref int[] a)

    {

        for(int i = (a.Length -1)/2; i > 0 ; i--)

        {

            Heapify(ref a, i);

        }

    }

    private static void Heapify(ref int[] a, int i)

    {

        var left = Left(i);

        var right = Right(i);

        var largest = i;

        if(left <= a.Length -1 && a[left] > a[largest]) largest = left;

        if(right <= a.Length -1 && a[right] > a[largest]) largest = right;

        if(largest != i)

        {

            swap(ref a, i, largest);

            Heapify(ref a, largest);

        }

    }

    private static void swap(ref int[] a, int source, int dest)

    {

        var temp = a[source];

        a[source] = a[dest];

        a[dest] = temp;

    }

    private static int Left(int i)

    {

        return 2 * i;

    }

    private static int Right(int i)

    {

        return (2 * i) + 1;

    }

}