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using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
namespace aoc2019
{
internal class Day3 : Day
{
public override int DayNumber => 3;
private readonly IEnumerable<(int, int)> intersections;
private readonly List<Dictionary<(int, int), int>> wires;
public Day3()
{
wires = Input.Select(ParseWire).ToList();
intersections = wires[0].Keys.Intersect(wires[1].Keys);
}
public override string Part1()
{
return $"{intersections.Min(x => Math.Abs(x.Item1) + Math.Abs(x.Item2))}";
}
public override string Part2()
{
// add 2 to count (0, 0) on both lines
return $"{intersections.Min(x => wires[0][x] + wires[1][x]) + 2}";
}
private static Dictionary<(int, int), int> ParseWire(string line)
{
var r = new Dictionary<(int, int), int>();
int x = 0, y = 0, c = 0, i;
foreach (var step in line.Split(','))
{
var d = int.Parse(step.Substring(1));
switch (step[0])
{
case 'U': for (i = 0; i < d; i++) r.TryAdd((x, ++y), c++); break;
case 'D': for (i = 0; i < d; i++) r.TryAdd((x, --y), c++); break;
case 'R': for (i = 0; i < d; i++) r.TryAdd((++x, y), c++); break;
case 'L': for (i = 0; i < d; i++) r.TryAdd((--x, y), c++); break;
}
}
return r;
}
}
}
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