Advent of code day 8

day8.c3

@@ -0,0 +1,149 @@
+module day8;
+import std::array::list;
+import std::io;
+
+define Forest = distinct List<char[]>;
+fn Forest* parse_forest()
+{
+	File f;
+	f.open("forest.txt", "rb")!!;
+	defer catch(f.close());
+	Forest* forest = mem::alloc(Forest);
+	forest.init(512);
+	while (!f.eof())
+	{
+		char[] line = f.tgetline();
+		assert(line.len);
+		forest.append(line);
+	}
+	return forest;
+}
+
+fn int Forest.is_visible(Forest* this, int x, int y)
+{
+	if (x == 0 || y == 0) return 5;
+	isz last_y = this.len() - 1;
+	if (y == last_y) return 5;
+	isz last_x = this.get(0).len - 1;
+	if (x == last_x) return 5;
+	char[] row = this.get(y);
+	char height = row[x];
+	int directions_seen_from = 0;
+	do FROM_WEST: {
+		for (isz fx = 0; fx < x; fx++)
+        {
+            if (row[fx] >= height) break FROM_WEST;
+        }
+        return 1;
+	};
+	do FROM_EAST: {
+		for (isz fx = last_x; fx > x; fx--)
+        {
+            if (row[fx] >= height) break FROM_EAST;
+        }
+        return 2;
+	};
+	do FROM_NORTH: {
+		for (isz fy = 0; fy < y; fy++)
+        {
+            if (this.get(fy)[x] >= height) break FROM_NORTH;
+        }
+        return 3;
+	};
+	do FROM_SOUTH: {
+		for (isz fy = last_y; fy > y; fy--)
+        {
+            if (this.get(fy)[x] >= height) break FROM_SOUTH;
+        }
+        return 4;
+	};
+	return 0;
+}
+
+fn int Forest.scenic_score(Forest* this, int x, int y)
+{
+	isz last_y = this.len() - 1;
+	isz last_x = this.get(0).len - 1;
+	char[] row = this.get(y);
+	char height = row[x];
+	int scenic_score;
+	int score = 0;
+	for (isz fx = x - 1; fx >= 0; fx--)
+    {
+        score++;
+        if (row[fx] >= height) break;
+    }
+    scenic_score = score;
+    score = 0;
+	for (isz fx = x + 1; fx <= last_x; fx++)
+    {
+        score++;
+        if (row[fx] >= height) break;
+    }
+    scenic_score *= score;
+    score = 0;
+	for (isz fy = y - 1; fy >= 0; fy--)
+	{
+		score++;
+        if (this.get(fy)[x] >= height) break;
+	}
+    scenic_score *= score;
+    score = 0;
+	for (isz fy = y + 1; fy <= last_y; fy++)
+	{
+		score++;
+        if (this.get(fy)[x] >= height) break;
+	}
+	return scenic_score * score;
+}
+
+fn int Forest.visible_from_outside(Forest* forest)
+{
+	int width = forest.get(0).len;
+	int height = (int)forest.len();
+	int sum;
+	for (int y = 0; y < height; y++)
+	{
+		char[] line = forest.get(y);
+		assert(line.len == width);
+		for (int x = 0; x < width; x++)
+		{
+			int seen = forest.is_visible(x, y);
+			if (seen > 0) sum++;
+		}
+	}
+	return sum;
+}
+
+fn int Forest.best_scenic_score(Forest* forest)
+{
+	int width = forest.get(0).len;
+	int height = (int)forest.len();
+	int best_scenic_score;
+	for (int y = 0; y < height; y++)
+	{
+		for (int x = 0; x < width; x++)
+		{
+			int score = forest.scenic_score(x, y);
+			if (score > best_scenic_score) best_scenic_score = score;
+		}
+	}
+	return best_scenic_score;
+}
+
+fn void part1(Forest* forest)
+{
+	io::printfln("Visible from outside: %d", forest.visible_from_outside());
+}
+
+fn void part2(Forest* forest)
+{
+	io::printfln("Best scenic score: %d", forest.best_scenic_score());
+}
+
+fn void main()
+{
+	Forest* forest = parse_forest();
+	part1(forest);
+	part2(forest);
+}

forest.txt

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