Day 10: Hoof It
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- What is this?: Here is a post with a large amount of details: https://programming.dev/post/6637268
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2 points
Nice to have a really simple one for a change, both my day 1 and 2 solutions worked on their very first attempts.
I rewrote the code to combine the two though, since the implementations were almost identical for both solutions, and also to replace the recursion with a search list instead.
C#
int[] heights = new int[0];
(int, int) size = (0, 0);
public void Input(IEnumerable<string> lines)
{
size = (lines.First().Length, lines.Count());
heights = string.Concat(lines).Select(c => int.Parse(c.ToString())).ToArray();
}
int trails = 0, trailheads = 0;
public void PreCalc()
{
for (int y = 0; y < size.Item2; ++y)
for (int x = 0; x < size.Item1; ++x)
if (heights[y * size.Item1 + x] == 0)
{
var unique = new HashSet<(int, int)>();
trails += CountTrails((x, y), unique);
trailheads += unique.Count;
}
}
public void Part1()
{
Console.WriteLine($"Trailheads: {trailheads}");
}
public void Part2()
{
Console.WriteLine($"Trails: {trails}");
}
int CountTrails((int, int) from, HashSet<(int,int)> unique)
{
int found = 0;
List<(int,int)> toSearch = new List<(int, int)>();
toSearch.Add(from);
while (toSearch.Any())
{
var cur = toSearch.First();
toSearch.RemoveAt(0);
int height = heights[cur.Item2 * size.Item1 + cur.Item1];
for (int y = -1; y <= 1; ++y)
for (int x = -1; x <= 1; ++x)
{
if ((y != 0 && x != 0) || (y == 0 && x == 0))
continue;
var newAt = (cur.Item1 + x, cur.Item2 + y);
if (newAt.Item1 < 0 || newAt.Item1 >= size.Item1 || newAt.Item2 < 0 || newAt.Item2 >= size.Item2)
continue;
int newHeight = heights[newAt.Item2 * size.Item1 + newAt.Item1];
if (newHeight - height != 1)
continue;
if (newHeight == 9)
{
unique.Add(newAt);
found++;
continue;
}
toSearch.Add(newAt);
}
}
return found;
}
