Solution Review: Convert Max-Heap to Min-Heap

using System;
using System.Collections.Generic;
namespace chapter_8
{
    class exercise_1
    {
        static void minHeapify(List<int> h, int i)
        {
            int lc = i * 2 + 1;
            int rc = i * 2 + 2;
            int imin = i;
            if (lc < h.Count && (h[lc].CompareTo(h[imin]) < 0))
                imin = lc;
            if (rc < h.Count && (h[rc].CompareTo(h[imin]) < 0))
                imin = rc;
            if (i != imin)
            {
                int temp = h[i];
                h[i] = h[imin];
                h[imin] = temp;
                minHeapify(h,imin);
            }
        }
        static List<int> buildMinHeap(List<int> heapList)
        {
            for (int i = (heapList.Count - 1) / 2; i > -1; i--)
            {
                minHeapify(heapList, i);
            }
            return heapList;
        }
        static string convertMax(List<int> maxHeap)
        {
            string result = "";
            maxHeap = buildMinHeap(maxHeap);
            for (int i = 0; i < maxHeap.Count; i++)
            {
                if (i == maxHeap.Count - 1)
                    result += maxHeap[i].ToString();
                else
                    result += maxHeap[i].ToString() + ",";
            }
            return result;
        }
        static void Main(string[] args)
        {
            List<int> heapList = new List<int>{ 9, 4, 7, 1, -2, 6, 5 };
            Console.Write(convertMax(heapList));
            return;
        }
    }
}