48 lines
1.5 KiB
C#
48 lines
1.5 KiB
C#
namespace AOC2022;
|
|
|
|
/// <summary>
|
|
/// Day 9: <a href="https://adventofcode.com/2022/day/9"/>
|
|
/// </summary>
|
|
public sealed class Day09() : Day(2022, 9, "Rope Bridge")
|
|
{
|
|
private List<(char direction, int count)>? _steps;
|
|
|
|
public override void ProcessInput() =>
|
|
_steps = Input.Select(line => (line[0], int.Parse(line[2..]))).ToList();
|
|
|
|
private int CountTailPositions(int ropeLength)
|
|
{
|
|
var rope = Enumerable.Range(0, ropeLength).Select(_ => (x: 0, y: 0)).ToArray();
|
|
var visited = new HashSet<(int x, int y)>();
|
|
|
|
foreach (var step in _steps!.SelectMany(step => Enumerable.Range(0, step.count), (step, _) => step))
|
|
{
|
|
switch (step.direction)
|
|
{
|
|
case 'U': rope[0].y++; break;
|
|
case 'D': rope[0].y--; break;
|
|
case 'L': rope[0].x--; break;
|
|
case 'R': rope[0].x++; break;
|
|
}
|
|
|
|
foreach (var i in Enumerable.Range(1, ropeLength - 1))
|
|
{
|
|
int dx = rope[i - 1].x - rope[i].x, dy = rope[i - 1].y - rope[i].y;
|
|
if (Math.Max(Math.Abs(dx), Math.Abs(dy)) > 1)
|
|
{
|
|
rope[i].x += Math.Sign(dx);
|
|
rope[i].y += Math.Sign(dy);
|
|
}
|
|
}
|
|
|
|
visited.Add(rope.Last());
|
|
}
|
|
|
|
return visited.Count;
|
|
}
|
|
|
|
public override object Part1() => CountTailPositions(2);
|
|
|
|
public override object Part2() => CountTailPositions(10);
|
|
}
|