75 lines
2.0 KiB
C#
75 lines
2.0 KiB
C#
using MoreLinq;
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namespace aoc2021;
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/// <summary>
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/// Day 13: <see href="https://adventofcode.com/2021/day/13"/>
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/// </summary>
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public sealed class Day13 : Day
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{
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private List<(int x, int y)> _dots;
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private readonly List<(char axis, int index)> _folds;
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public Day13() : base(13, "Transparent Origami")
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{
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var s = Input.Split("").ToList();
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_dots = s[0].Select(p =>
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{
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var i = p.Split(',', 2).Select(int.Parse).ToList();
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return (i[0], i[1]);
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}).ToList();
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_folds = s[1].Select(p => p.Split(' ').Skip(2).First()).Select(p =>
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{
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var i = p.Split('=', 2);
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return (i[0][0], int.Parse(i[1]));
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}).ToList();
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}
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private static List<(int x, int y)> DoFold(List<(int x, int y)> grid, char axis, int at)
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{
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List<(int, int)> result = new();
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switch (axis)
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{
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case 'x':
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foreach (var (x, y) in grid) result.Add((x > at ? 2 * at - x : x, y));
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break;
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case 'y':
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foreach (var (x, y) in grid) result.Add((x, y > at ? 2 * at - y : y));
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break;
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default: throw new ArgumentException("invalid fold axis", nameof(axis));
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}
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return result.Distinct().ToList();
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}
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private string PrintGrid()
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{
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var xMax = _dots.Max(g => g.x);
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var yMax = _dots.Max(g => g.y);
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var s = new StringBuilder();
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for (var y = 0; y <= yMax; y++)
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{
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for (var x = 0; x <= xMax; x++)
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s.Append(_dots.Contains((x, y)) ? "█" : "▒");
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s.AppendLine();
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}
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return s.ToString();
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}
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public override object Part1() =>
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DoFold(_dots, _folds[0].axis, _folds[0].index).Count;
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public override object Part2()
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{
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foreach (var (axis, at) in _folds)
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_dots = DoFold(_dots, axis, at);
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return Environment.NewLine + PrintGrid();
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}
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} |