interval merging

Program.cs

using static System.Diagnostics.Debug;
using static System.Math;
using Intervals = System.Collections.Generic.List<(int Start, int End)>;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            // Setup.
            var input = new Intervals { (1, 4), (8, 10), (3, 6) };
            var output = new Intervals();
            var expectedOutput = new Intervals { (1, 6), (8, 10) };

            // Sort.
            input.Sort((a, b) => a.Start.CompareTo(b.Start));

            // Merge.
            (int Start, int End)? mergedInterval = null;
            foreach (var interval in input)
            {
                if (mergedInterval == null)
                {
                    mergedInterval = interval;
                }
                else if (interval.Start > mergedInterval.Value.End)
                {
                    output.Add(mergedInterval.Value);
                    mergedInterval = interval;
                }
                else
                {
                    mergedInterval = (
                        mergedInterval.Value.Start,
                        Max(mergedInterval.Value.End, interval.End)
                    );
                }
            }
            if (mergedInterval.HasValue)
                output.Add(mergedInterval.Value);

            // Assert.
            Assert(expectedOutput.Count == output.Count);
            for (int i = 0; i < output.Count; i++)
                Assert(expectedOutput[i] == output[i]);
        }
    }
}