123 lines
3 KiB
C#
123 lines
3 KiB
C#
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var boards = new List<Board>();
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using var sr = new StreamReader("../inputs/day04.txt");
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var lines = sr.ReadToEnd().Split("\n").Select(x => x.Trim()).ToList();
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var numbers = lines.First().Split(",").Select(x => Convert.ToByte(x)).ToList();
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lines.RemoveAt(0); //Drop numbers
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lines.RemoveAt(0); //Drop whitespace
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var currentBoard = new List<string>();
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foreach (var line in lines)
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{
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if (!string.IsNullOrEmpty(line))
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{
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currentBoard.Add(line);
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}
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else
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{
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boards.Add(new Board(currentBoard));
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currentBoard = new List<string>();
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}
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}
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var part1Done = false;
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foreach (var number in numbers)
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{
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foreach (var board in boards)
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board.Mark(number);
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var winningBoards =
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boards.Where(board => board.Win).ToArray(); // Need to enumerate this before the loop or it will break
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foreach (var board in winningBoards)
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{
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if (!part1Done)
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{
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Console.WriteLine($"2021 Day 04 Part 1 result: {board.Score * number}");
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part1Done = true;
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}
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if (boards.Count == 1)
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Console.WriteLine($"2021 Day 04 Part 2 result: {board.Score * number}");
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boards.Remove(board);
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}
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if (!boards.Any())
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break;
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}
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private class Board
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{
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private readonly byte?[,] _rows;
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internal int Score => _rows.Cast<byte?>().Aggregate(0, (score, number) => score + (number ?? 0));
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private bool HorizontalWin => DidRowWin(_rows);
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private bool VerticalWin => DidRowWin(Transpose());
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internal bool Win => HorizontalWin || VerticalWin;
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internal Board(IEnumerable<string> inputRows)
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{
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_rows = new byte?[5, 5];
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for (var r = 0; r < inputRows.Count(); r++)
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{
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var nums = inputRows
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.ElementAt(r)
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.Split(" ")
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.Where(x => !string.IsNullOrEmpty(x))
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.Select(x => Convert.ToByte(x));
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for (var c = 0; c < nums.Count(); c++)
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{
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_rows[c, r] = nums.ElementAt(c);
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}
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}
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}
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internal void Mark(byte number)
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{
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for (var r = 0; r < _rows.GetLength(0); r++)
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{
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for (var c = 0; c < _rows.GetLength(1); c++)
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{
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if (_rows[c, r].HasValue && _rows[c, r].Value == number)
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_rows[c, r] = null;
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}
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}
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}
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private byte?[,] Transpose()
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{
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var cols = new byte?[5, 5];
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for (var c = 0; c < 5; c++)
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{
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for (var r = 0; r < 5; r++)
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{
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cols[c, r] = _rows[r, c];
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}
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}
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return cols;
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}
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private static bool DidRowWin(byte?[,] rows)
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{
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var win = true;
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for (var r = 0; r < rows.GetLength(0); r++)
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{
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win = true;
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for (var c = 0; c < rows.GetLength(1); c++)
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{
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if (rows[c, r].HasValue)
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win = false;
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}
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if (win)
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break;
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}
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return win;
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}
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}
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