AOC2023: Implement day23 part1

My day22 implementation is off by couple of bricks...

userspace/aoc2023/CMakeLists.txt

@@ -24,6 +24,7 @@ set(AOC2023_PROJECTS
 	day19
 	day20
 	day21
+	day23
 	full
 )
 

userspace/aoc2023/day23/CMakeLists.txt

@@ -0,0 +1,22 @@
+cmake_minimum_required(VERSION 3.26)
+
+project(aoc2023_day23 CXX)
+
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2023_day23 ${SOURCES})
+target_compile_options(aoc2023_day23 PUBLIC -O2 -g)
+target_link_libraries(aoc2023_day23 PUBLIC libc ban)
+
+add_dependencies(aoc2023_day23 libc-install ban-install)
+
+add_custom_target(aoc2023_day23-install
+	COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/aoc2023_day23 ${BANAN_AOC2023_BIN}/day23
+	DEPENDS aoc2023_day23
+	DEPENDS aoc2023_always
+)
+
+add_dependencies(aoc2023 aoc2023_day23)
+add_dependencies(aoc2023-install aoc2023_day23-install)

userspace/aoc2023/day23/main.cpp

@@ -0,0 +1,156 @@
+#include <BAN/Array.h>
+#include <BAN/ScopeGuard.h>
+#include <BAN/StringView.h>
+#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;
+
+BAN::Vector<BAN::Vector<char>> parse_grid(FILE* fp)
+{
+	BAN::Vector<BAN::Vector<char>> grid;
+
+	char buffer[256];
+	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;
+		
+		MUST(grid.emplace_back(line.size(), '\0'));
+		for (size_t i = 0; i < line.size(); i++)
+			grid.back()[i] = line[i];
+	}
+
+	return grid;
+}
+
+struct Position
+{
+	i64 x, y;
+
+	Position operator+(const Position& other) const
+	{
+		return { .x = x + other.x, .y = y + other.y };
+	}
+
+	bool operator==(const Position& other) const
+	{
+		return x == other.x && y == other.y;
+	}
+};
+
+i64 recurse_grid(BAN::Vector<Position>& path, const BAN::Vector<BAN::Vector<char>>& grid)
+{
+	const auto entry = path.back();
+	BAN::ScopeGuard _([&] { while (path.back() != entry) path.pop_back(); });
+
+	while (path.back().y < (i64)grid.size() - 1)
+	{
+		BAN::Array<Position, 4> valid_next;
+		size_t valid_next_count = 0;
+
+		constexpr Position offsets[4] { { -1, 0 }, { 1, 0 }, { 0, -1 }, { 0, 1 } };
+		for (size_t i = 0; i < 4; i++)
+		{
+			auto next = path.back() + offsets[i];
+			if (next.y < 0 || next.y >= (i64)grid.size())
+				continue;
+			if (next.x < 0 || next.x >= (i64)grid.front().size())
+				continue;
+			switch (grid[next.y][next.x])
+			{
+				case '^': next.y--; break;
+				case 'v': next.y++; break;
+				case '<': next.x--; break;
+				case '>': next.x++; break;
+				case '#': continue;
+			}
+			if (path.contains(next))
+				continue;
+			valid_next[valid_next_count++] = next;
+		}
+
+		if (valid_next_count == 0)
+			return 0;
+		
+		if (valid_next_count == 1)
+		{
+			MUST(path.push_back(valid_next.front()));
+			continue;
+		}
+
+		i64 result = 0;
+		for (size_t i = 0; i < valid_next_count; i++)
+		{
+			MUST(path.push_back(valid_next[i]));
+			result = BAN::Math::max(result, recurse_grid(path, grid));
+			path.pop_back();
+		}
+		return result;
+	}
+
+	i64 result = 0;
+	for (size_t i = 1; i < path.size(); i++)
+		result += BAN::Math::abs(path[i - 1].x - path[i].x) + BAN::Math::abs(path[i - 1].y - path[i].y);
+	return result;
+}
+
+i64 puzzle1(FILE* fp)
+{
+	auto grid = parse_grid(fp);
+
+	BAN::Vector<Position> path;
+	for (i64 x = 0; x < (i64)grid.front().size(); x++)
+	{
+		if (grid.front()[x] == '.')
+		{
+			MUST(path.push_back({ .x = x, .y = 0 }));
+			break;
+		}
+	}
+
+	return recurse_grid(path, grid);
+}
+
+i64 puzzle2(FILE* fp)
+{
+	(void)fp;
+	return -1;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2023/day23_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

@@ -4,8 +4,10 @@
 
 int main()
 {
-	for (int i = 1; i <= 21; i++)
+	for (int i = 1; i <= 23; i++)
 	{
+		if (i == 22)
+			continue;
 		printf("day %d:\n", i);
 
 		char command[128];