using System;

using System.Net.Http;

using System.Linq;

​

// Get data

var response = await new HttpClient().GetStringAsync("https://tompafireadventofcode.free.beeceptor.com/day7");

var positions = response.Split(',').Select(int.Parse);

​

var posibleEndPositions = Enumerable.Range(positions.Min(), positions.Max() - positions.Min());

​

var positionsWithStepsToNPosition = positions.SelectMany(p => posibleEndPositions.Select(p2 => new { start = p, end = p2, steps = Math.Abs(p2 - p) }));

​

// Step 1

​

var endPositionWithFewestTotalSteps = positionsWithStepsToNPosition

    .GroupBy(p => p.end)

    .Select(x => new { end = x.Key, totalSteps = x.Sum(y => y.steps) })

    .MinBy(x => x.totalSteps);

​

Console.WriteLine($"Shortest number of steps: {endPositionWithFewestTotalSteps.totalSteps} (to position {endPositionWithFewestTotalSteps.end})");

​

// Step 2

​

var fuelConsumptionForSteps = positionsWithStepsToNPosition.Select(p => p.steps).Distinct()

    .ToDictionary(steps => steps, steps => GetFuelConsumtion(steps));

​

var endPositionWithLowestFuelConsumption = positionsWithStepsToNPosition

    .GroupBy(p => p.end)

    .Select(x => new { end = x.Key, fuelConsumption = x.Sum(y => fuelConsumptionForSteps[y.steps]) })

    .MinBy(x => x.fuelConsumption);

​

Console.WriteLine($"Lowest fuel consumption: {endPositionWithLowestFuelConsumption.fuelConsumption} (to position {endPositionWithLowestFuelConsumption.end})");

​

​

int GetFuelConsumtion(int steps)

{

    var fuel = 0;

​

    for (var i = 1; i <= steps; i++)

    {

        fuel += i;

    }

​

    return fuel;

}

​