AOC2023: Implement day24 part1

userspace/aoc2023/CMakeLists.txt

@@ -25,6 +25,7 @@ set(AOC2023_PROJECTS
 	day20
 	day21
 	day23
+	day24
 	full
 )
 

userspace/aoc2023/day24/CMakeLists.txt

@@ -0,0 +1,22 @@
+cmake_minimum_required(VERSION 3.26)
+
+project(aoc2023_day24 CXX)
+
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2023_day24 ${SOURCES})
+target_compile_options(aoc2023_day24 PUBLIC -O2 -g)
+target_link_libraries(aoc2023_day24 PUBLIC libc ban)
+
+add_dependencies(aoc2023_day24 libc-install ban-install)
+
+add_custom_target(aoc2023_day24-install
+	COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/aoc2023_day24 ${BANAN_AOC2023_BIN}/day24
+	DEPENDS aoc2023_day24
+	DEPENDS aoc2023_always
+)
+
+add_dependencies(aoc2023 aoc2023_day24)
+add_dependencies(aoc2023-install aoc2023_day24-install)

userspace/aoc2023/day24/main.cpp

@@ -0,0 +1,138 @@
+#include <BAN/Vector.h>
+
+#include <ctype.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 Hailstone
+{
+	double px, py, pz;
+	double vx, vy, vz;
+};
+
+i64 parse_i64(BAN::StringView str)
+{
+	while (isspace(str.front()))
+		str = str.substring(1);
+	bool negative = str.front() == '-';
+	if (negative)
+		str = str.substring(1);
+	i64 result = 0;
+	for (char c : str)
+		if (isdigit(c))
+			result = (result * 10) + (c - '0');
+	return negative ? -result : result;
+}
+
+BAN::Vector<Hailstone> parse_hailstones(FILE* fp)
+{
+	BAN::Vector<Hailstone> hailstones;
+
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		BAN::StringView line(buffer);
+		ASSERT(line.back() == '\n');
+		line = line.substring(0, line.size() - 1);
+		if (line.empty())
+			break;
+		
+		auto position_velocity_strs = MUST(line.split('@'));
+		ASSERT(position_velocity_strs.size() == 2);
+
+		Hailstone hailstone;
+
+		auto position_strs = MUST(position_velocity_strs[0].split(','));
+		ASSERT(position_strs.size() == 3);
+		hailstone.px = parse_i64(position_strs[0]);
+		hailstone.py = parse_i64(position_strs[1]);
+		hailstone.pz = parse_i64(position_strs[2]);
+
+		auto velocity_strs = MUST(position_velocity_strs[1].split(','));
+		ASSERT(velocity_strs.size() == 3);
+		hailstone.vx = parse_i64(velocity_strs[0]);
+		hailstone.vy = parse_i64(velocity_strs[1]);
+		hailstone.vz = parse_i64(velocity_strs[2]);
+
+		MUST(hailstones.push_back(hailstone));
+	}
+
+	return hailstones;
+}
+
+i64 puzzle1(FILE* fp)
+{
+	auto hailstones = parse_hailstones(fp);
+	
+	i64 result = 0;
+
+	for (size_t i = 0; i < hailstones.size(); i++)
+	{
+		for (size_t j = i + 1; j < hailstones.size(); j++)
+		{
+			const auto& h1 = hailstones[i];
+			const auto& h2 = hailstones[j];
+
+			// skip parallel lines
+			if (h1.vy * h2.vx == h2.vy * h1.vx)
+				continue;
+
+			const double t2 = ((h2.py - h1.py) * h1.vx - (h2.px - h1.px) * h1.vy) / (h2.vx * h1.vy - h1.vx * h2.vy);
+			if (t2 < 0.0)
+				continue;
+
+			const double t1 = ((h2.py - h1.py) + t2 * h2.vy) / h1.vy;
+			if (t1 < 0.0)
+				continue;
+
+			const double x = h2.px + t2 * h2.vx;
+			const double y = h2.py + t2 * h2.vy;
+
+			constexpr double min = 200000000000000.0;
+			constexpr double max = 400000000000000.0;
+			if ((min <= x && x <= max) && (min <= y && y <= max))
+				result++;
+		}
+	}
+
+	return result;
+}
+
+i64 puzzle2(FILE* fp)
+{
+	(void)fp;
+	return -1;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2023/day24_input.txt";
+
+	if (argc >= 2)
+		file_path = argv[1];
+
+	FILE* fp = fopen(file_path, "r");
+	if (fp == nullptr)
+	{
+		perror("fopen");
+		return 1;
+	}
+
+	printf("puzzle1: %" PRId64 "\n", puzzle1(fp));
+
+	fseek(fp, 0, SEEK_SET);
+
+	printf("puzzle2: %" PRId64 "\n", puzzle2(fp));
+
+	fclose(fp);
+}

userspace/aoc2023/full/main.cpp

@@ -4,7 +4,7 @@
 
 int main()
 {
-	for (int i = 1; i <= 23; i++)
+	for (int i = 1; i <= 24; i++)
 	{
 		if (i == 22)
 			continue;