day 1 pt.2

src/AdventOfCode/AdventOfCode/Day1.cs

@@ -1,11 +1,56 @@
 using System.Buffers;
 using System.IO.Pipelines;
 using System.Text;
+using System.Text.RegularExpressions;
 
 namespace AdventOfCode;
 
-public static class Day1
+public static partial class Day1
 {
+    [GeneratedRegex(pattern: "0", RegexOptions.Compiled | RegexOptions.IgnoreCase)]
+    private static partial Regex Zero();
+    
+    [GeneratedRegex(pattern: "one|1", RegexOptions.Compiled | RegexOptions.IgnoreCase)]
+    private static partial Regex One();
+    
+    [GeneratedRegex(pattern: "two|2", RegexOptions.Compiled | RegexOptions.IgnoreCase)]
+    private static partial Regex Two();
+    
+    [GeneratedRegex(pattern: "three|3", RegexOptions.Compiled | RegexOptions.IgnoreCase)]
+    private static partial Regex Three();
+    
+    [GeneratedRegex(pattern: "four|4", RegexOptions.Compiled | RegexOptions.IgnoreCase)]
+    private static partial Regex Four();
+    
+    [GeneratedRegex(pattern: "five|5", RegexOptions.Compiled | RegexOptions.IgnoreCase)]
+    private static partial Regex Five();
+    
+    [GeneratedRegex(pattern: "six|6", RegexOptions.Compiled | RegexOptions.IgnoreCase)]
+    private static partial Regex Six();
+    
+    [GeneratedRegex(pattern: "seven|7", RegexOptions.Compiled | RegexOptions.IgnoreCase)]
+    private static partial Regex Seven();
+    
+    [GeneratedRegex(pattern: "eight|8", RegexOptions.Compiled | RegexOptions.IgnoreCase)]
+    private static partial Regex Eight();
+    
+    [GeneratedRegex(pattern: "nine|9", RegexOptions.Compiled | RegexOptions.IgnoreCase)]
+    private static partial Regex Nine();
+
+    private static readonly Dictionary<Regex, int> matchers = new()
+    {
+        { Zero(), 0 },
+        { One(), 1 },
+        { Two(), 2 },
+        { Three(), 3 },
+        { Four(), 4 },
+        { Five(), 5 },
+        { Six(), 6 },
+        { Seven(), 7 },
+        { Eight(), 8 },
+        { Nine(), 9 },
+    };
+    
     public class Result
     {
         public int Sum;
@@ -121,27 +166,67 @@ public static class Day1
     /// <returns></returns>
     public static int ParseString(string str)
     {
-        var numOfDigits = 0;
-        char? firstDigit = default;
-        char? lastDigit = default;
+        var strSpan = str.AsSpan();
+        int? firstDigit = default;
+        int? lastDigit = default;
 
-        foreach (var ch in str)
+        for (var index = 0; index < strSpan.Length; index++)
         {
-            if (!int.TryParse($"{ch}", out _))
+            var span = strSpan[0 .. (index + 1)];
+            if (span.IsEmpty)
             {
                 continue;
             }
 
-            numOfDigits++;
-            firstDigit ??= ch;
-            lastDigit = ch;
+            foreach (var kv in matchers)
+            {
+                if (!kv.Key.IsMatch(span))
+                {
+                    continue;
                 }
                 
-        if (firstDigit == null || lastDigit == null || numOfDigits < 1)
+                firstDigit ??= kv.Value;
+                break;
+            }
+
+            if (firstDigit != null)
+            {
+                break;
+            }
+        }
+
+        for (var i = strSpan.Length - 1; i >= 0; i--)
+        {
+            var span = strSpan[i .. strSpan.Length];
+            if (span.IsEmpty)
+            {
+                continue;
+            }
+            
+            foreach (var kv in matchers)
+            {
+                if (!kv.Key.IsMatch(span))
+                {
+                    continue;
+                }
+                
+                lastDigit ??= kv.Value;
+                break;
+            }
+            
+            if (lastDigit != null)
+            {
+                break;
+            }
+        }
+
+        if (firstDigit == null)
         {
             return 0;
         }
 
+        lastDigit ??= firstDigit;
+        
         return !int.TryParse($"{firstDigit.Value}{lastDigit.Value}", out var result)
             ? 0
             : result;

src/AdventOfCode/ConsoleApp/Program.cs

@@ -1,6 +1,10 @@
 // See https://aka.ms/new-console-template for more information
 
+using System.Diagnostics;
 using AdventOfCode;
 
+var sw = Stopwatch.StartNew();
 var day1Result = await Day1.ExecuteAsync("input.txt");
 Console.WriteLine($"Advent of code: Day 1 result: {day1Result}");
+sw.Stop();
+Console.WriteLine($"Advent of code: Day 1 time: {sw.Elapsed.TotalMilliseconds} ms.");