laatzen/Common/CommonConsole/Program.cs

using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace CommonConsole
{
    public class Program
    {
        public static void Main()
        {
            var aggregatedValues = new Dictionary<double, double[]>();

            foreach (var line in File.ReadAllLines("test.txt"))
            {
                if (string.IsNullOrWhiteSpace(line))
                {
                    continue;
                }

                var tokens = line.Split(new[] { '\t', ' ' }, StringSplitOptions.RemoveEmptyEntries);

                if (tokens.Length != 2)
                {
                    continue;
                }

                if (!double.TryParse(tokens[0], out var temperature) || !double.TryParse(tokens[1], out var timeOfFlight))
                {
                    continue;
                }

                if (temperature < 0 || temperature > 40 || timeOfFlight < 0 || timeOfFlight > 1)
                {
                    continue;
                }

                if (!aggregatedValues.ContainsKey(temperature))
                {
                    aggregatedValues[temperature] = new [] { double.MaxValue, double.MinValue };
                }

                var values = aggregatedValues[temperature];

                if (values[0] > timeOfFlight)
                {
                    values[0] = timeOfFlight;
                }

                if (values[1] < timeOfFlight)
                {
                    values[1] = timeOfFlight;
                }
            }

            File.WriteAllText("test.json", JsonConvert.SerializeObject(aggregatedValues
                .Select(x => new double[] { x.Key, x.Value[0], x.Value[1] })
                .ToArray(), Formatting.Indented));
        }
    }
}