[2k25] Add day 3

Days/Day3.cs

@@ -0,0 +1,120 @@
+using Spectre.Console;
+
+namespace AdventOfCode.Days;
+
+public class Day3 : Day
+{
+    public override int Number => 3;
+    public override string Name => "Lobby";
+
+    public override void RunPart1(bool display = true)
+    {
+        var totalOutputJoltage = 0L;
+
+        Span<int> bank = stackalloc int[100];
+
+        foreach (var line in Input.EnumerateLines())
+        {
+            // Parse the line into battery values
+            for (var i = 0; i < bank.Length; i++)
+            {
+                bank[i] = line[i] - '0';
+            }
+
+            // The first digit the joltage value will be the "left-most" biggest number we can find
+            var firstDigitMax = bank[0];
+            var firstDigitMaxIndex = 0;
+
+            for (var i = 1; i < bank.Length - 1; i++)
+            {
+                var batteryValue = bank[i];
+                if (batteryValue > firstDigitMax)
+                {
+                    firstDigitMax = batteryValue;
+                    firstDigitMaxIndex = i;
+
+                    // We cannot have a digit bigger than 9
+                    if (batteryValue is 9)
+                    {
+                        break;
+                    }
+                }
+            }
+
+            // Now we can find the second digit which will be the biggest digit on the right of the first one
+            var secondDigitMax = bank[firstDigitMaxIndex + 1];
+            for (var i = firstDigitMaxIndex + 2; i < bank.Length; i++)
+            {
+                var batteryValue = bank[i];
+
+                if (batteryValue > secondDigitMax)
+                {
+                    secondDigitMax = batteryValue;
+
+                    if (batteryValue is 9)
+                    {
+                        break;
+                    }
+                }
+            }
+
+            // Build the joltage value
+            totalOutputJoltage += firstDigitMax * 10 + secondDigitMax;
+        }
+
+        if (display)
+        {
+            AnsiConsole.MarkupLine($"[green]The total output joltage is: [yellow]{totalOutputJoltage}[/][/]");
+        }
+    }
+
+    public override void RunPart2(bool display = true)
+    {
+        var totalOutputJoltage = 0L;
+
+        Span<int> bank = stackalloc int[100];
+
+        foreach (var line in Input.EnumerateLines())
+        {
+            // Parse the line into battery values
+            for (var i = 0; i < bank.Length; i++)
+            {
+                bank[i] = line[i] - '0';
+            }
+
+            var maxIndex = -1;
+            for (var digitPosition = 11; digitPosition >= 0; digitPosition--)
+            {
+                // Next max is always on the right of previous one
+                maxIndex++;
+
+                // Find biggest battery value on the right
+                var max = bank[maxIndex];
+                for (var i = maxIndex + 1; i < bank.Length - digitPosition; i++)
+                {
+                    var batteryValue = bank[i];
+
+                    if (batteryValue > max)
+                    {
+                        maxIndex = i;
+                        max = batteryValue;
+
+                        // We cannot have a digit bigger than 9
+                        if (batteryValue is 9)
+                        {
+                            break;
+                        }
+                    }
+                }
+
+                // Directly add its value to the total, we don't need to do compound sum
+                totalOutputJoltage += max * (long) Math.Pow(10, digitPosition);
+            }
+        }
+
+        if (display)
+        {
+            AnsiConsole.MarkupLine($"[green]The total output joltage is: [yellow]{totalOutputJoltage}[/][/]");
+        }
+    }
+}