day 3 part 1

aoc2021.test/DayTests.cs

@@ -6,6 +6,7 @@ public class DayTests
     [DataTestMethod]
     [DataRow(typeof(Day01), "1616", "1645")]
     [DataRow(typeof(Day02), "2272262", "2134882034")]
+    [DataRow(typeof(Day03), "3009600", "")]
     public void CheckAllDays(Type dayType, string part1, string part2)
     {
         var s = Stopwatch.StartNew();
@@ -38,6 +39,7 @@ public class DayTests
     [DataTestMethod]
     [DataRow(typeof(Day01), "7", "5")]
     [DataRow(typeof(Day02), "150", "900")]
+    [DataRow(typeof(Day03), "198", "230")]
     public void CheckTestInputs(Type dayType, string part1, string part2)
     {
         Day.UseTestInput = true;

aoc2021/Day03.cs

@@ -0,0 +1,38 @@
+namespace aoc2021;
+
+/// <summary>
+/// Day 3: <see href="https://adventofcode.com/2021/day/3"/>
+/// </summary>
+public sealed class Day03 : Day
+{
+    private readonly List<string> _report;
+    
+    public Day03() : base(3, "Binary Diagnostic")
+    {
+        _report = Input.ToList();
+    }
+
+    public override string Part1()
+    {
+        var l = _report.Count / 2;
+        var g = new StringBuilder();
+        var e = new StringBuilder();
+        
+        foreach (var i in Enumerable.Range(0, _report[0].Length))
+        {
+            var ones = _report.Select(r => r[i]).Count(c => c == '1');
+            g.Append(ones > l ? '1' : '0');
+            e.Append(ones > l ? '0' : '1');
+        }
+
+        var gamma   = Convert.ToInt32(g.ToString(), 2);
+        var epsilon = Convert.ToInt32(e.ToString(), 2);
+
+        return $"{gamma * epsilon}";
+    }
+
+    public override string Part2()
+    {
+        return "";
+    }
+}

aoc2021/input/test03.in

@@ -0,0 +1,12 @@
+00100
+11110
+10110
+10111
+10101
+01111
+00111
+11100
+10000
+11001
+00010
+01010