MinSegmentTree.cs

using System;

namespace AlgorithmsAndDataStructures.DataStructures.SegmentTree
{
    public class MinSegmentTree : AbstractSegmentTree
    {
        public MinSegmentTree(int[] input)
            :base(input, Math.Min)
        {

        }

        protected override int DummyValue { get; set; } = int.MaxValue;

        public void Update(int index, int value)
        {
            UpdateInternal(0, 0, OriginalInputLength - 1, index, value);
        }

        private int UpdateInternal(int currentPosition, int currentStart, int currentEnd, int index, int value)
        {
            if (currentStart == currentEnd && currentStart == index)
            {
                Tree[currentPosition] = value;
                return Tree[currentPosition];
            }

            if (index > currentEnd || index < currentStart)
            {
                return Tree[currentPosition];
            }

            var middle = currentStart + (currentEnd - currentStart) / 2;

            Tree[currentPosition] = Math.Min(UpdateInternal(currentPosition * 2 + 1, currentStart, middle, index, value),
                UpdateInternal(currentPosition * 2 + 2, middle + 1, currentEnd, index, value));

            return Tree[currentPosition];
        }
    }
}