Solve 2024 day 7

Author: Basje

2024.Tests/Day07Tests.cs

@@ -0,0 +1,48 @@
+using Basje.AdventOfCode.Y2024.D07;
+
+namespace Basje.AdventOfCode.Y2024.Tests;
+
+public static class Day07Tests
+{
+    [Fact]
+    public static void Part1()
+    {
+        var solution = new Day07();
+        const string input = """
+                             190: 10 19
+                             3267: 81 40 27
+                             83: 17 5
+                             156: 15 6
+                             7290: 6 8 6 15
+                             161011: 16 10 13
+                             192: 17 8 14
+                             21037: 9 7 18 13
+                             292: 11 6 16 20
+                             """;
+
+        var answer = solution.SolvePart1(input);
+
+        answer.Should().Be(3749);
+    }
+
+    [Fact]
+    public static void Part2()
+    {
+        var solution = new Day07();
+        const string input = """
+                             190: 10 19
+                             3267: 81 40 27
+                             83: 17 5
+                             156: 15 6
+                             7290: 6 8 6 15
+                             161011: 16 10 13
+                             192: 17 8 14
+                             21037: 9 7 18 13
+                             292: 11 6 16 20
+                             """;
+        
+        var answer = solution.SolvePart2(input);
+        
+        answer.Should().Be(11387);
+    }
+}

2024/D07/Day07.cs

@@ -0,0 +1,90 @@
+using Basje.AdventOfCode.Y2024.Toolbox.Grid;
+
+namespace Basje.AdventOfCode.Y2024.D07;
+
+public class Day07 : Solution<long[][]>
+{
+    protected override long[][] ParseInput(string input)
+    {
+        return input
+            .PerLine()
+            .IgnoreEmptyLines()
+            .Select(line => line.Split(": ".ToArray(), StringSplitOptions.RemoveEmptyEntries))
+            .Select(line => line.Select(long.Parse).ToArray())
+            .ToArray();
+    }
+
+    protected override object SolvePart1(long[][] equations)
+    {
+        long sum = 0;
+
+        foreach (var equation in equations)
+        {
+            var test = equation.First();
+            var values = CalculateTestValues(equation.Skip(1).Take(1).ToList(), equation.Skip(2).ToList());
+
+            if (values.Contains(test))
+            {
+                sum += test;
+            }
+        }
+
+        return sum;
+    }
+
+    protected override object SolvePart2(long[][] equations)
+    {
+        long sum = 0;
+
+        foreach (var equation in equations)
+        {
+            var test = equation.First();
+            var values = CalculateTestValues2(equation.Skip(1).Take(1).ToList(), equation.Skip(2).ToList());
+
+            if (values.Contains(test))
+            {
+                sum += test;
+            }
+        }
+
+        return sum;
+    }
+
+    private List<long> CalculateTestValues(List<long> values, List<long> input)
+    {
+        if (input.Count == 0) return values;
+
+        List<long> newValues = [];
+        var firstInput = input.First();
+
+        foreach (var number in values)
+        {
+            newValues.Add(number + firstInput); 
+            newValues.Add(number * firstInput);
+        }
+
+        return CalculateTestValues(newValues, input.Skip(1).ToList());
+    }
+    
+    private List<long> CalculateTestValues2(List<long> values, List<long> input)
+    {
+        if (input.Count == 0) return values;
+
+        List<long> newValues = [];
+        var firstInput = input.First();
+
+        foreach (var number in values)
+        {
+            newValues.Add(number + firstInput); 
+            newValues.Add(number * firstInput);
+            newValues.Add(long.Parse($"{number}{firstInput}"));
+        }
+
+        return CalculateTestValues2(newValues, input.Skip(1).ToList());
+    }
+}
+
+internal static class Day07Extensions
+{
+
+}