aoc2024: Implement day10 solution

userspace/aoc2024/CMakeLists.txt

@@ -8,6 +8,7 @@ set(AOC2024_PROJECTS
 	day7
 	day8
 	day9
+	day10
 	full
 )
 

userspace/aoc2024/day10/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2024_day10 ${SOURCES})
+banan_include_headers(aoc2024_day10 ban)
+banan_link_library(aoc2024_day10 libc)
+
+install(TARGETS aoc2024_day10 OPTIONAL)

userspace/aoc2024/day10/main.cpp

@@ -0,0 +1,171 @@
+#include <BAN/HashSet.h>
+#include <BAN/Vector.h>
+
+#include <inttypes.h>
+#include <stdio.h>
+
+using i8  = int8_t;
+using i16 = int16_t;
+using i32 = int32_t;
+using i64 = int64_t;
+using isize = ssize_t;
+
+using u8  = uint8_t;
+using u16 = uint16_t;
+using u32 = uint32_t;
+using u64 = uint64_t;
+using usize = size_t;
+
+struct Position
+{
+	u32 x, y;
+
+	constexpr bool operator==(const Position& other) const
+	{
+		return x == other.x && y == other.y;
+	}
+};
+
+struct PositionHash
+{
+	constexpr BAN::hash_t operator()(Position state) const
+	{
+		return BAN::hash<u64>{}((u64)state.x << 32 | (u64)state.y);
+	}
+};
+
+struct Grid2D
+{
+	usize width { 0 };
+	usize height { 0 };
+	BAN::Vector<char> data;
+
+	inline char get(usize x, usize y) const
+	{
+		ASSERT(x < width && y < height);
+		return data[y * width + x];
+	}
+};
+
+static Grid2D read_grid2d(FILE* fp)
+{
+	usize width { 0 };
+	usize height { 0 };
+	BAN::Vector<char> data;
+
+	char buffer[1024];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		const usize len = strlen(buffer);
+		if (len == 0 || buffer[0] == '\n')
+			break;
+		if (data.empty())
+			width = len - 1;
+		height++;
+
+		ASSERT(buffer[width] == '\n');
+
+		if (data.capacity() < height * width)
+			MUST(data.reserve(2 * height * width));
+
+		MUST(data.resize(height * width));
+		memcpy(&data[(height - 1) * width], buffer, width);
+	}
+
+	(void)data.shrink_to_fit();
+
+	return Grid2D {
+		.width = width,
+		.height = height,
+		.data = BAN::move(data),
+	};
+}
+
+i64 get_trailhead_score(const Grid2D& map, u32 x, u32 y, char curr, BAN::HashSet<Position, PositionHash>& trail_ends, bool allow_duplicate)
+{
+	if (x >= map.width)
+		return 0;
+	if (y >= map.height)
+		return 0;
+
+	if (map.get(x, y) != curr)
+		return 0;
+	if (curr == '9')
+	{
+		const auto pos = Position { .x = x, .y = y };
+		if (trail_ends.contains(pos))
+			return allow_duplicate;
+		MUST(trail_ends.insert(Position { .x = x, .y = y }));
+		return 1;
+	}
+
+	i64 result = 0;
+	result += get_trailhead_score(map, x - 1, y,     curr + 1, trail_ends, allow_duplicate);
+	result += get_trailhead_score(map, x,     y - 1, curr + 1, trail_ends, allow_duplicate);
+	result += get_trailhead_score(map, x + 1, y,     curr + 1, trail_ends, allow_duplicate);
+	result += get_trailhead_score(map, x,     y + 1, curr + 1, trail_ends, allow_duplicate);
+	return result;
+}
+
+i64 part1(FILE* fp)
+{
+	auto map = read_grid2d(fp);
+
+	i64 result = 0;
+
+	for (u32 y = 0; y < map.height; y++)
+	{
+		for (u32 x = 0; x < map.width; x++)
+		{
+			if (map.get(x, y) != '0')
+				continue;
+			BAN::HashSet<Position, PositionHash> trail_ends;
+			result += get_trailhead_score(map, x, y, '0', trail_ends, false);
+		}
+	}
+
+	return result;
+}
+
+i64 part2(FILE* fp)
+{
+	auto map = read_grid2d(fp);
+
+	i64 result = 0;
+
+	for (u32 y = 0; y < map.height; y++)
+	{
+		for (u32 x = 0; x < map.width; x++)
+		{
+			if (map.get(x, y) != '0')
+				continue;
+			BAN::HashSet<Position, PositionHash> trail_ends;
+			result += get_trailhead_score(map, x, y, '0', trail_ends, true);
+		}
+	}
+
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2024/day10_input.txt";
+
+	if (argc >= 2)
+		file_path = argv[1];
+
+	FILE* fp = fopen(file_path, "r");
+	if (fp == nullptr)
+	{
+		perror("fopen");
+		return 1;
+	}
+
+	printf("part1: %" PRId64 "\n", part1(fp));
+
+	fseek(fp, 0, SEEK_SET);
+
+	printf("part2: %" PRId64 "\n", part2(fp));
+
+	fclose(fp);
+}