feat: solve day 7 part 1 and part 2

07/BridgeRepair/Equation.cs

@@ -0,0 +1,76 @@
+namespace BridgeRepair;
+
+// TODO: Look at what the public API should be here.
+class Equation(long testValue, List<long> numbers)
+{
+  public readonly long TestValue = testValue;
+
+  public bool IsPossible(bool isPart2 = false)
+  {
+    var configs = GeneratePossibleOperatorConfigurations(isPart2).ToList();
+    return configs.Select(Evaluate).Any(result => result == TestValue);
+  }
+
+  public long Evaluate(char[] operators)
+  {
+    var result = numbers[0];
+
+    for (var i = 0; i < operators.Length; i++)
+    {
+      var currentOperator = operators[i];
+      var number = numbers[i + 1];
+
+      if (currentOperator is '+')
+      {
+        result += number;
+        continue;
+      }
+
+      if (currentOperator is '*')
+      {
+        result *= number;
+        continue;
+      }
+
+      result = long.Parse(result + number.ToString());
+    }
+    
+    return result;
+  }
+  
+  public IEnumerable<char[]> GeneratePossibleOperatorConfigurations(bool isPart2 = false)
+  {
+    // TODO: make it possible to pass is operators we can use.
+    var numberOfPositions = numbers.Count - 1;
+    var config = new char[numberOfPositions];
+    var numOfOperators = isPart2 ? 3 : 2;
+    var numberOfPossibleConfigurations = Math.Pow(numOfOperators, numberOfPositions);
+
+    for (var i = 0; i < numberOfPossibleConfigurations; i++)
+    {
+      var j = 0;
+      
+      while (j < numberOfPositions)
+      {
+        var currentOperator = config[j];
+        
+        if (currentOperator is '+')
+        {
+          config[j] = '*';
+          break;
+        }
+
+        if (isPart2 && currentOperator is '*')
+        {
+          config[j] = '|';
+          break;
+        }
+
+        config[j] = '+';
+        j++;
+      }
+      
+      yield return config.ToArray();
+    }
+  }
+}

07/BridgeRepair/Program.cs

@@ -1,5 +1,7 @@
 using System.Diagnostics;
 
+using BridgeRepair;
+
 if (args.Length is 0)
 {
   Console.WriteLine("Please provide a path to the input file.");
@@ -18,7 +20,9 @@ var input = await File.ReadAllLinesAsync(args[0]);
 var stopwatch = new Stopwatch();
 stopwatch.Start();
 
-// TODO: Implement solution
+var result = new PuzzleParser().Parse(input)
+  .Where(e => e.IsPossible(isPart2))
+  .Sum(e => e.TestValue);
 
 stopwatch.Stop();
-Console.WriteLine($". ({stopwatch.ElapsedMilliseconds}ms)");
+Console.WriteLine($"The sum of the test value for possible equations is {result}. ({stopwatch.ElapsedMilliseconds}ms)");

07/BridgeRepair/PuzzleParser.cs

@@ -0,0 +1,9 @@
+namespace BridgeRepair;
+
+class PuzzleParser
+{
+  public List<Equation> Parse(string[] input)
+  {
+    return input.Select(s => s.ToEquation()).ToList();
+  }
+}

07/BridgeRepair/StringExtensions.cs

@@ -0,0 +1,14 @@
+namespace BridgeRepair;
+
+static class StringExtensions
+{
+  public static Equation ToEquation(this string line)
+  {
+    var parts = line.Split(':');
+    var testValue = long.Parse(parts[0]);
+    var numbers = parts[1].Split(" ", StringSplitOptions.RemoveEmptyEntries)
+      .Select(long.Parse)
+      .ToList();
+    return new(testValue, numbers);
+  }
+}