aoc2024: Implement day14 solution

userspace/aoc2024/CMakeLists.txt

@@ -12,6 +12,7 @@ set(AOC2024_PROJECTS
 	day11
 	day12
 	day13
+	day14
 	full
 )
 

userspace/aoc2024/day14/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2024_day14 ${SOURCES})
+banan_include_headers(aoc2024_day14 ban)
+banan_link_library(aoc2024_day14 libc)
+
+install(TARGETS aoc2024_day14 OPTIONAL)

userspace/aoc2024/day14/main.cpp

@@ -0,0 +1,152 @@
+#include <BAN/Array.h>
+#include <BAN/Vector.h>
+
+#include <fcntl.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <sys/framebuffer.h>
+#include <sys/mman.h>
+#include <termios.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;
+
+i64 part1(FILE* fp)
+{
+	i32 quadrants[4] {};
+
+	for (;;)
+	{
+		i32 px, py, vx, vy;
+		if (fscanf(fp, "p=%" SCNd32 ",%" SCNd32 " v=%" SCNd32 ",%" SCNd32 "\n", &px, &py, &vx, &vy) != 4)
+			break;
+
+		const i32 tx = (((px + 100 * vx) % 101) + 101) % 101;
+		const i32 ty = (((py + 100 * vy) % 103) + 103) % 103;
+
+		if (tx < 50 && ty < 51)
+			quadrants[0]++;
+		if (tx > 50 && ty < 51)
+			quadrants[1]++;
+		if (tx < 50 && ty > 51)
+			quadrants[2]++;
+		if (tx > 50 && ty > 51)
+			quadrants[3]++;
+	}
+
+	return quadrants[0] * quadrants[1] * quadrants[2] * quadrants[3];
+}
+
+struct Robot
+{
+	i32 px, py;
+	i32 vx, vy;
+};
+
+usize largest_area(const BAN::Vector<Robot>& robots)
+{
+	BAN::Array<bool, 101 * 103> robot_map(false);
+	for (const auto& robot : robots)
+		robot_map[robot.py * 101 + robot.px] = true;
+
+	BAN::Array<bool, 101 * 103> checked(false);
+
+	usize result = 0;
+	for (i32 y = 0; y < 103; y++)
+	{
+		for (i32 x = 0; x < 101; x++)
+		{
+			if (checked[y * 101 + x])
+				continue;
+			if (!robot_map[y * 101 + x])
+				continue;
+
+			struct Position { i32 x, y; };
+			BAN::Vector<Position> to_check;
+			MUST(to_check.reserve(101 * 103));
+
+			MUST(to_check.emplace_back(x, y));
+
+			usize area = 0;
+			while (!to_check.empty())
+			{
+				const auto pos = to_check.back();
+				to_check.pop_back();
+
+				if (checked[pos.y * 101 + pos.x])
+					continue;
+				checked[pos.y * 101 + pos.x] = true;
+
+				if (!robot_map[pos.y * 101 + pos.x])
+					continue;
+
+				area++;
+
+				if (pos.x - 1 >=  0) MUST(to_check.emplace_back(pos.x - 1, pos.y    ));
+				if (pos.x + 1 < 101) MUST(to_check.emplace_back(pos.x + 1, pos.y    ));
+				if (pos.y - 1 >=  0) MUST(to_check.emplace_back(pos.x,     pos.y - 1));
+				if (pos.y + 1 < 103) MUST(to_check.emplace_back(pos.x,     pos.y + 1));
+			}
+
+			result = BAN::Math::max(result, area);
+		}
+	}
+
+	return result;
+}
+
+i64 part2(FILE* fp)
+{
+	BAN::Vector<Robot> robots;
+
+	for (;;)
+	{
+		i32 px, py, vx, vy;
+		if (fscanf(fp, "p=%" SCNd32 ",%" SCNd32 " v=%" SCNd32 ",%" SCNd32 "\n", &px, &py, &vx, &vy) != 4)
+			break;
+		MUST(robots.emplace_back(px, py, vx, vy));
+	}
+
+	for (i64 frame = 0;; frame++)
+	{
+		if (largest_area(robots) >= robots.size() / 4)
+			return frame;
+		for (auto& robot : robots)
+		{
+			robot.px = (((robot.px + robot.vx) % 101) + 101) % 101;
+			robot.py = (((robot.py + robot.vy) % 103) + 103) % 103;
+		}
+	}
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2024/day14_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);
+}