Day 3

With thanks to my best friend Regex

src/03.cs

@@ -0,0 +1,58 @@
+using System.Text.RegularExpressions;
+
+namespace aoc2024;
+
+internal class Day03 : Day
+{
+    private string instructions = string.Empty;
+    internal override void Parse()
+    {
+        // instructions = "xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))";
+        // instructions = "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))";
+        instructions = Util.Parsing.ReadAllText(GetDay());
+    }
+
+    internal override string Part1()
+    {
+        List<(long, long)> mults = [];
+        var regex = new Regex(@"mul\((\d+),(\d+)\)", RegexOptions.Compiled);
+        foreach (var match in regex.Matches(instructions))
+        {
+            var num1 = long.Parse(((Match)match).Groups[1].Value);
+            var num2 = long.Parse(((Match)match).Groups[2].Value);
+            mults.Add((num1, num2));
+        }
+
+        var total = mults.Sum(m => m.Item1 * m.Item2);
+
+        return $"Instruction result: <+white>{total}";
+    }
+
+    internal override string Part2()
+    {
+        bool enabled = true;
+        List<(long, long)> mults = [];
+        var regex = new Regex(@"do\(\)|don't\(\)|mul\((\d+),(\d+)\)", RegexOptions.Compiled);
+        foreach (var match in regex.Matches(instructions))
+        {
+            if (((Match) match).Groups[0].Value == "do()")
+            {
+                enabled = true;
+            }
+            else if (((Match) match).Groups[0].Value == "don't()")
+            {
+                enabled = false;
+            }
+            else if (enabled)
+            {
+                var num1 = long.Parse(((Match) match).Groups[1].Value);
+                var num2 = long.Parse(((Match) match).Groups[2].Value);
+                mults.Add((num1, num2));
+            }
+        }
+
+        var total = mults.Sum(m => m.Item1 * m.Item2);
+
+        return $"Enabled instruction result: <+white>{total}";
+    }
+}