advent_of_code_2024/Level1/Level1Solver.cs

namespace AoC24;

using AoC24.Common;
using AoCLevelInputProvider;
using Parsing;
using Parsing.Schema;

public class Level1Solver : FullTextLevelSolverBase
{
    public override int LevelNumber
    {
        get { return 1; }
    }

    protected override InputSchemaBuilder DefineInputSchema(InputSchemaBuilder schemaBuilder)
    {
        return schemaBuilder
                    .Repeat(2)
                        .Expect(InputType.Integer)
                    .EndRepetition();
    }

    public override string SolveFirstStar()
    {
        var data = this.GetData()
                       .AsListColumns<int>();

        var sortedLeftColumn = data[0];
        sortedLeftColumn.Sort();
        var sortedRightColumn = data[1];
        sortedRightColumn.Sort();

        var sumDifferences = 0;

        for (var i = 0; i < sortedLeftColumn.Count; i++)
        {
            sumDifferences += Math.Abs(sortedLeftColumn[i]-sortedRightColumn[i]);
        }

        return sumDifferences.ToString();
    }

    public override string SolveSecondStar()
    {
        var data = this.GetData()
                       .AsListColumns<int>();

        var uniqueLeftColumn = data[0].Distinct();
        var rightColumn = data[1];
        
        Dictionary<int, int> numInstances = new Dictionary<int, int>();
        foreach(var value in uniqueLeftColumn)
        {
            numInstances[value] = 0;
        }

        foreach(var value in rightColumn)
        {
            if (numInstances.ContainsKey(value))
            {
                numInstances[value] = numInstances[value] + 1;
            }
        }

        var sumScore = 0;

        foreach(var key in numInstances.Keys)
        {
            sumScore = sumScore + numInstances[key] * key;
        }

        return sumScore.ToString();
    }
}