1 files changed, 63 insertions, 0 deletions
diff --git a/aoc2021/Day10.cs b/aoc2021/Day10.cs
new file mode 100644
index 0000000..4907a80
--- /dev/null
+++ b/aoc2021/Day10.cs
@@ -0,0 +1,63 @@
+using System.Collections;
+
+namespace aoc2021;
+
+/// <summary>
+/// Day 10: <see href="https://adventofcode.com/2021/day/10"/>
+/// </summary>
+public sealed class Day10 : Day
+{
+    private readonly List<string> _input;
+    private readonly char[] _openers = { '(', '[', '{', '<' };
+    private readonly char[] _closers = { ')', ']', '}', '>' };
+
+    private readonly Dictionary<char, int> _scores = new()
+    {
+        { ')', 3 },
+        { ']', 57 },
+        { '}', 1197 },
+        { '>', 25137 }
+    };
+
+    private readonly Dictionary<char, int> _scoresClosing = new()
+    {
+        { '(', 1 },
+        { '[', 2 },
+        { '{', 3 },
+        { '<', 4 }
+    };
+    
+    public Day10() : base(10, "Syntax Scoring")
+    {
+        _input = Input.ToList();
+    }
+
+    public override string Part1()
+    {
+        var s = new Stack<char>();
+        var score = 0;
+        foreach (var line in _input)
+        {
+            foreach (var c in line)
+            {
+                if (_openers.Contains(c))
+                {
+                    s.Push(c);
+                }
+                else
+                {
+                    var y = s.Pop();
+                    if (Math.Abs(y - c) <= 3) continue;
+                    score += _scores[c];
+                    break;
+                }
+            }
+        }
+
+        return score.ToString();
+    }
+
+    public override string Part2()
+    {
+    }
+}