day 2 pt 1; day 3

AdventOfCode/Problems/AOC2025/Day2/GiftShop.cs

@@ -1,6 +1,8 @@
 using System;
 using System.Collections.Generic;
+using System.Data;
 using System.Reflection.Metadata;
+using System.Security.Cryptography;
 using System.Text;
 
 using ZLinq;
@@ -13,14 +15,64 @@ internal class GiftShop : Problem<long, long>
 	private IdRange[] _ranges = [];
 	public override void CalculatePart1()
 	{
-		throw new NotImplementedException();
+		var v = _ranges.SelectMany(GetDoubleSequences);
+		//Console.WriteLine(v.AsJoinedString());
+		Part1 = v.Sum();
 	}
 
-	public static List<long> GetDoubleSequences(IdRange range)
+	public static long[] GetDoubleSequences(IdRange range)
 	{
+		range = range.Snap();
 		var minDigits = range.Min.DigitCount() / 2;
 		var maxDigits = range.Max.DigitCount() / 2;
-		throw new NotImplementedException();
+
+		var min = GetMinValue((int)minDigits, range.Min);
+		var max = GetMaxValue((int)maxDigits, range.Max);
+		//Console.WriteLine($"{min}-{max}");
+		if (max < min)
+			return [];
+		var n = (max - min) + 1;
+		var result = new long[n];
+		for (long i = min; i <= max; i++)
+		{
+			result[i - min] = (i * QuickMath.FastPow10(minDigits)) + i;
+		}
+		return result;
+	}
+
+	public static long SnapToUpNearestValidRange(long value)
+	{
+		var dc = value.DigitCount();
+		if (dc.IsEven())
+			return value;
+		return QuickMath.FastPow10(dc);
+	}
+	public static long SnapToDownNearestValidRange(long value)
+	{
+		var dc = value.DigitCount();
+		if (dc.IsEven())
+			return value;
+		return QuickMath.FastPow10(dc - 1) - 1;
+	}
+
+	public static long GetMinValue(int digits, long value)
+	{
+		var val = long.Parse(value.ToString()[..^digits]);
+		while ((val * QuickMath.FastPow10(digits)) + val < value)
+		{
+			val++;
+		}
+		return val;
+	}
+
+	public static long GetMaxValue(int digits, long value)
+	{
+		var val = long.Parse(value.ToString()[..^digits]);
+		while ((val * QuickMath.FastPow10(digits)) + val > value)
+		{
+			val--;
+		}
+		return val;
 	}
 
 	public override void CalculatePart2()
@@ -30,13 +82,19 @@ internal class GiftShop : Problem<long, long>
 
 	public override void LoadInput()
 	{
-		var text = ReadInputText("sample.txt");
+		var text = ReadInputText("input.txt");
 		_ranges = text.Split(',')
 			.AsValueEnumerable()
-			.Select(r => r.Split('-').Select(int.Parse))
+			.Select(r => r.Split('-').Select(long.Parse))
 			.Select(r => new IdRange(r.First(), r.Last()))
 			.ToArray();
 	}
 
-	public record IdRange(int Min, int Max);
+	public record IdRange(long Min, long Max)
+	{
+		public IdRange Snap()
+		{
+			return new IdRange(SnapToUpNearestValidRange(Min), SnapToDownNearestValidRange(Max));
+		}
+	}
 }

AdventOfCode/Problems/AOC2025/Day3/Lobby.cs

@@ -0,0 +1,65 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+using ZLinq;
+
+namespace AdventOfCode.Problems.AOC2025.Day3;
+
+[ProblemInfo(2025, 3, "Lobby")]
+internal class Lobby : Problem<long, long>
+{
+	private (int val, int idx)[][] _batteryBanks = [];
+
+	public override void CalculatePart1()
+	{
+		Part1 = _batteryBanks.AsValueEnumerable().Select(bank =>
+		{
+			var batteries = GetViableBatteries(bank);
+			return GetPower(batteries);
+		}).Sum();
+	}
+
+
+	public override void CalculatePart2()
+	{
+		Console.WriteLine();
+		var b = _batteryBanks.AsValueEnumerable().Select(bank =>
+		{
+			var batteries = GetViableBatteries(bank, 12);
+			return GetPower(batteries);
+		});
+		Part2 = b.Sum();
+	}
+
+	public static long GetPower(int[] values)
+	{
+		return values.Select((v, idx) =>
+		{
+			var mag = (long)Math.Pow(10, values.Length - idx - 1);
+			return v * mag;
+		}).Sum();
+	}
+
+	public static int[] GetViableBatteries((int val, int idx)[] source, int count = 2)
+	{
+		var batteries = new int[count];
+		var offset = 0;
+		for (int i = count; i > 0; i--)
+		{
+			var tgt = i - 1;
+			var (val, idx) = source[offset..^tgt].MaxBy(v => v.val);
+			offset = idx + 1;
+			batteries[count - i] = val;
+		}
+		return batteries;
+	}
+
+	public override void LoadInput()
+	{
+		_batteryBanks = ReadInputLines("input.txt")
+			.AsValueEnumerable()
+			.Select(l => l.AsValueEnumerable().Select((v, idx) => (v - '0', idx)).ToArray())
+			.ToArray();
+	}
+}

AdventOfCode/Program.cs

@@ -4,4 +4,4 @@ global using AdventOfCode.Utils;
 
 
 var runner = new AOCRunner();
-runner.RenderInteractiveMenu();
+runner.WithDay(2).RenderInteractiveMenu();

AdventOfCode/Runner/ExtraMath.cs

@@ -44,4 +44,14 @@ public static class ExtraMath
 		else
 			return remainder;
 	}
+
+	public static bool IsEven<T>(this T value) where T : INumber<T>
+	{
+		return T.IsEvenInteger(value);
+	}
+
+	public static bool IsOdd<T>(this T value) where T : INumber<T>
+	{
+		return T.IsOddInteger(value);
+	}
 }