Add day 7

Day7/Program.cs

@@ -0,0 +1,90 @@
+var lines = File.ReadLines("input.txt");
+
+List<(long, List<long>)> equationList = new();
+
+foreach (var line in lines)
+{
+    var splitLine = line.Split(":");
+    var item1 = long.Parse(splitLine[0]);
+    var item2 = splitLine[1].Split(" ").Where(x => x != String.Empty).Select(long.Parse).ToList();
+    equationList.Add((item1, item2));
+}
+
+var part1 = EquationSolver(equationList, ['+', '*']);
+var part2 = EquationSolver(equationList, ['+', '*', '|']);
+
+Console.WriteLine($"Part1: {part1}\nPart2: {part2}");
+
+long EquationSolver(List<(long, List<long>)> equations, List<char> possibleOperators)
+{
+    long numberOfPossibleEquations = 0;
+    
+    // For thread safety
+    var lockObject = new object();
+    
+    Parallel.ForEach(equations, equation =>
+    {
+        var operatorCombinations = GetCombinations(possibleOperators.ToArray(), equation.Item2.Count - 1);
+        var foundValidCombination = false;
+        
+        Parallel.ForEach(operatorCombinations, (operatorCombination, state) =>
+        {
+            if (!IsEquationPossible(equation.Item1, equation.Item2, operatorCombination)) return;
+            
+            lock (lockObject)
+            {
+                foundValidCombination = true;
+            }
+            state.Break();
+        });
+
+        if (!foundValidCombination) return;
+        
+        lock (lockObject)
+        {
+            numberOfPossibleEquations += equation.Item1;
+        }
+    });
+
+    return numberOfPossibleEquations;
+}
+bool IsEquationPossible(long result, List<long> parameters, char[] operators)
+{
+    var calculatedResult = parameters[0];
+
+    for (var i = 0; i <= operators.Length - 1; i++)
+    {
+        calculatedResult = operators[i] switch
+        {
+            '+' => calculatedResult + parameters[i + 1],
+            '*' => calculatedResult * parameters[i + 1],
+            '|' => long.Parse($"{calculatedResult}{parameters[i + 1]}"),
+            _ => throw new Exception("Invalid operator")
+        };
+    }
+
+    return calculatedResult == result;
+}
+
+List<char[]> GetCombinations(char[] chars, int length)
+{
+    var result = new List<char[]>();
+    GenerateCombinations(chars, length, [], result);
+    return result;
+}
+
+void GenerateCombinations(char[] chars, int length, List<char> current, List<char[]> result)
+{
+    if (length == 0)
+    {
+        result.Add(current.ToArray());
+        return;
+    }
+
+    foreach (var c in chars)
+    {
+        current.Add(c);
+        GenerateCombinations(chars, length - 1, current, result);
+        current.RemoveAt(current.Count - 1);
+    }
+}