Heap sort of string in place instead of insertion sort

HeapSort.cs

// https://www.hackertouch.com/csharp-generic-heap-sort.html

using System;

public static class HeapSortMethods
{
    public static void HeapSort(string[] a)
    {
        // build binary heap from all items
        for (int i = 0; i < a.Length; i++)
        {
            int index = i;
            var s = a[i]; // use next item

            // and move it on top, if greater than parent
            while (index > 0 && a[(index - 1) / 2].CompareTo(s) < 0)
            {
                int top = (index - 1) / 2;
                a[index] = a[top];
                index = top;
            }
            a[index] = s;
        }

        for (int i = a.Length - 1; i > 0; i--)
        {
            // delete max and place it as last
            var last = a[i];
            a[i] = a[0];

            int index = 0;
            // the last one positioned in the heap
            while (index * 2 + 1 < i)
            {
                int left = index * 2 + 1, right = left + 1;
                if (right < i && a[left].CompareTo(a[right]) < 0)
                {
                    if (last.CompareTo(a[right]) > 0)
						break;
                    a[index] = a[right];
                    index = right;
                }
                else
                {
                    if (last.CompareTo(a[left]) > 0)
						break;
                    a[index] = a[left];
                    index = left;
                }
            }
            a[index] = last;
        }
    }
}

public class Program
{
    public static void Main()
    {
        string[] testList = { "US", "UK", "JPN", "CAN", "PAK", "IND" };
        HeapSortMethods.HeapSort(testList);
        foreach (var t in testList)
        {
            Console.WriteLine(t);
        }
    }
}