103 lines
3.5 KiB
C#
103 lines
3.5 KiB
C#
using AdventOfCode.Utils.Extensions;
|
|
|
|
namespace AdventOfCode.Year2022;
|
|
|
|
public class Day9
|
|
{
|
|
public Day9()
|
|
{
|
|
var moves = new List<(char, int)>();
|
|
File.ReadAllLines("inputs/day9.txt").ToList().ForEach(line =>
|
|
{
|
|
var split = line.Split(" ");
|
|
moves.Add((Convert.ToChar(split[0]), Convert.ToInt32(split[1])));
|
|
});
|
|
Console.WriteLine($@"
|
|
Day9 Solution
|
|
Part1 Result: {GetPositionCount(moves, 2)}
|
|
Part2 Result: {GetPositionCount(moves, 10)}
|
|
|
|
=============================");
|
|
}
|
|
|
|
private static int GetPositionCount(List<(char, int)> moves, int knots)
|
|
{
|
|
var currentPositions = new List<List<int>>();
|
|
currentPositions.Fill(knots, new List<int>(new[] { 0, 0 }));
|
|
var tailHistory = new HashSet<(int, int)>();
|
|
|
|
foreach (var move in moves)
|
|
for (var moveN = 0; moveN < move.Item2; moveN++)
|
|
{
|
|
var vector = GetVector(move.Item1);
|
|
var previousTailPosition = currentPositions[0].ToArray();
|
|
currentPositions[0] = UpdateHead(vector, currentPositions[0]);
|
|
for (var tailN = 0; tailN < knots - 1; tailN++)
|
|
{
|
|
var nextPreviousTailPosition = currentPositions[tailN + 1].ToArray();
|
|
currentPositions[tailN + 1] = UpdateTail(currentPositions[tailN], currentPositions[tailN + 1],
|
|
previousTailPosition);
|
|
previousTailPosition = nextPreviousTailPosition;
|
|
if (tailN == knots - 2)
|
|
tailHistory.Add((currentPositions[knots - 1][0], currentPositions[knots - 1][1]));
|
|
}
|
|
}
|
|
|
|
return tailHistory.Count;
|
|
}
|
|
|
|
private static List<int> UpdateHead(int[] vector, List<int> currentPosition)
|
|
{
|
|
currentPosition[0] += vector[0];
|
|
currentPosition[1] += vector[1];
|
|
return new List<int> { currentPosition[0], currentPosition[1] };
|
|
}
|
|
|
|
private static List<int> UpdateTail(List<int> currentHeadPosition, List<int> currentTailPosition,
|
|
int[] previousTailPosition)
|
|
{
|
|
var head = new List<int>
|
|
{
|
|
currentHeadPosition[0] - previousTailPosition[0],
|
|
currentHeadPosition[1] - previousTailPosition[1]
|
|
};
|
|
|
|
if (Math.Abs(currentHeadPosition[0] - currentTailPosition[0]) > 1 ||
|
|
Math.Abs(currentHeadPosition[1] - currentTailPosition[1]) > 1)
|
|
{
|
|
if (previousTailPosition[0] == currentTailPosition[0] ||
|
|
previousTailPosition[1] == currentTailPosition[1])
|
|
return new List<int>
|
|
{
|
|
currentTailPosition[0] + head[0],
|
|
currentTailPosition[1] + head[1]
|
|
};
|
|
|
|
var difference = new List<int>
|
|
{
|
|
currentHeadPosition[0] - currentTailPosition[0],
|
|
currentHeadPosition[1] - currentTailPosition[1]
|
|
};
|
|
|
|
return new List<int>
|
|
{
|
|
currentTailPosition[0] + difference[0].Signal() * Math.Min(Math.Abs(difference[0]), 1),
|
|
currentTailPosition[1] + difference[1].Signal() * Math.Min(Math.Abs(difference[1]), 1)
|
|
};
|
|
}
|
|
|
|
return currentTailPosition;
|
|
}
|
|
|
|
private static int[] GetVector(char direction)
|
|
{
|
|
return direction switch
|
|
{
|
|
'U' => new[] { 1, 0 },
|
|
'D' => new[] { -1, 0 },
|
|
'R' => new[] { 0, 1 },
|
|
'L' => new[] { 0, -1 },
|
|
_ => new[] { 0, 0 }
|
|
};
|
|
}
|
|
} |