75 lines
2.3 KiB
C#
75 lines
2.3 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Drawing;
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using System.Linq;
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namespace aoc2019
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{
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internal class Day10 : Day
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{
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public override int DayNumber => 10;
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private readonly List<Point> asteroids = new List<Point>();
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private Point best = new Point(-1, -1);
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private IGrouping<double, Point>[] bestgroups;
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private int bestcansee;
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public Day10()
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{
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var starmap = Input.Select(x => x.Select(y => y == '#').ToArray()).ToArray();
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for (var i = 0; i < starmap.Length; i++)
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for (var j = 0; j < starmap[i].Length; j++)
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if (starmap[i][j])
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asteroids.Add(new Point(i, j));
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foreach (var asteroid in asteroids)
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{
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var groups = asteroids.Except(new[] { asteroid })
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.Select(a => new Point(a.X - asteroid.X, a.Y - asteroid.Y))
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.GroupBy(a => Math.Atan2(a.Y, a.X))
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.ToArray();
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var cansee = groups.Count();
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if (cansee > bestcansee)
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{
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best = asteroid;
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bestcansee = cansee;
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bestgroups = groups;
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}
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}
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}
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public override string Part1()
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{
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return $"{bestcansee}";
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}
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public override string Part2()
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{
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var removals = bestgroups
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.Select(g => new {
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Angle = g.Key,
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Targets = new Queue<Point>(g.OrderBy(a =>
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Math.Sqrt(Math.Pow(a.X - best.X, 2) + Math.Pow(a.Y - best.Y, 2))
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))
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})
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.OrderBy(g => g.Angle > Math.PI / 2)
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.ThenByDescending(g => g.Angle);
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var removed = 0;
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while (true)
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foreach (var removal in removals)
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if (removal.Targets.Count > 0)
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{
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var toremove = removal.Targets.Dequeue();
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removed++;
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if (removed == 200)
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{
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return $"{(toremove.X * 100) + toremove.Y}";
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}
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}
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}
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}
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}
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