aoc2024: Implement day8 solution

I did not feel like optimizing this one, so its a O(n^2) looking over
every cell in the grid. Performs way faster than my optimized day6
solution tho :DD

userspace/aoc2024/CMakeLists.txt

@@ -6,6 +6,7 @@ set(AOC2024_PROJECTS
 	day5
 	day6
 	day7
+	day8
 	full
 )
 

userspace/aoc2024/day8/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2024_day8 ${SOURCES})
+banan_include_headers(aoc2024_day8 ban)
+banan_link_library(aoc2024_day8 libc)
+
+install(TARGETS aoc2024_day8 OPTIONAL)

userspace/aoc2024/day8/main.cpp

@@ -0,0 +1,166 @@
+#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 u8  = uint8_t;
+using u16 = uint16_t;
+using u32 = uint32_t;
+using u64 = uint64_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);
+	}
+};
+
+static BAN::Vector<BAN::Vector<char>> parse_input(FILE* fp)
+{
+	BAN::Vector<BAN::Vector<char>> result;
+
+	char buffer[1024];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		if (!buffer[0] || buffer[0] == '\n')
+			break;
+
+		const size_t row_len = strlen(buffer) - 1;
+		ASSERT(buffer[row_len] == '\n');
+
+		if (!result.empty())
+			ASSERT(result.back().size() == row_len);
+
+		BAN::Vector<char> row;
+		MUST(row.resize(row_len));
+		memcpy(row.data(), buffer, row_len);
+
+		MUST(result.push_back(BAN::move(row)));
+	}
+
+	return result;
+}
+
+i64 part1(FILE* fp)
+{
+	auto input = parse_input(fp);
+
+	BAN::HashSet<Position, PositionHash> antinodes;
+
+	for (size_t y1 = 0; y1 < input.size(); y1++)
+	{
+		for (size_t x1 = 0; x1 < input[y1].size(); x1++)
+		{
+			if (input[y1][x1] == '.')
+				continue;
+
+			for (size_t y2 = y1; y2 < input.size(); y2++)
+			{
+				for (size_t x2 = (y2 == y1) ? x1 + 1 : 0; x2 < input[y2].size(); x2++)
+				{
+					if (input[y2][x2] != input[y1][x1])
+						continue;
+
+					const size_t x_diff = x2 - x1;
+					const size_t y_diff = y2 - y1;
+
+					auto antinode1 = Position { .x = (u32)(x1 - x_diff), .y = (u32)(y1 - y_diff) };
+					if (antinode1.y < input.size() && antinode1.x < input[antinode1.y].size())
+						MUST(antinodes.insert(antinode1));
+
+					auto antinode2 = Position { .x = (u32)(x2 + x_diff), .y = (u32)(y2 + y_diff) };
+					if (antinode2.y < input.size() && antinode2.x < input[antinode2.y].size())
+						MUST(antinodes.insert(antinode2));
+				}
+			}
+		}
+	}
+
+	return antinodes.size();
+}
+
+i64 part2(FILE* fp)
+{
+	auto input = parse_input(fp);
+
+	BAN::HashSet<Position, PositionHash> antinodes;
+
+	for (size_t y1 = 0; y1 < input.size(); y1++)
+	{
+		for (size_t x1 = 0; x1 < input[y1].size(); x1++)
+		{
+			if (input[y1][x1] == '.')
+				continue;
+
+			for (size_t y2 = y1; y2 < input.size(); y2++)
+			{
+				for (size_t x2 = (y2 == y1) ? x1 + 1 : 0; x2 < input[y2].size(); x2++)
+				{
+					if (input[y2][x2] != input[y1][x1])
+						continue;
+
+					const size_t x_diff = x2 - x1;
+					const size_t y_diff = y2 - y1;
+
+					for (size_t t = 0;; t++)
+					{
+						auto antinode = Position { .x = (u32)(x1 - t * x_diff), .y = (u32)(y1 - t * y_diff) };
+						if (antinode.y >= input.size() || antinode.x >= input[antinode.y].size())
+							break;
+						MUST(antinodes.insert(antinode));
+					}
+
+					for (size_t t = 0;; t++)
+					{
+						auto antinode = Position { .x = (u32)(x2 + t * x_diff), .y = (u32)(y2 + t * y_diff) };
+						if (antinode.y >= input.size() || antinode.x >= input[antinode.y].size())
+							break;
+						MUST(antinodes.insert(antinode));
+					}
+				}
+			}
+		}
+	}
+
+	return antinodes.size();
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2024/day8_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);
+}