aoc2024: Implement day19 solution

userspace/aoc2024/CMakeLists.txt

@@ -17,6 +17,7 @@ set(AOC2024_PROJECTS
 	day16
 	day17
 	day18
+	day19
 	full
 )
 

userspace/aoc2024/day19/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2024_day19 ${SOURCES})
+banan_link_library(aoc2024_day19 ban)
+banan_link_library(aoc2024_day19 libc)
+
+install(TARGETS aoc2024_day19 OPTIONAL)

userspace/aoc2024/day19/main.cpp

@@ -0,0 +1,162 @@
+#include <BAN/HashMap.h>
+#include <BAN/HashSet.h>
+#include <BAN/String.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 ParseInputResult
+{
+	BAN::Vector<BAN::String> available_towels;
+	BAN::Vector<BAN::String> target_patterns;
+};
+
+static ParseInputResult parse_input(FILE* fp)
+{
+	char buffer[128];
+
+	BAN::String first_line;
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		MUST(first_line.append(buffer));
+		if (first_line.back() != '\n')
+			continue;
+		first_line.pop_back();
+		break;
+	}
+
+	BAN::Vector<BAN::String> available_towels;
+	auto first_line_split = MUST(first_line.sv().split(','));
+	for (auto splitted : first_line_split)
+	{
+		if (splitted.starts_with(" "_sv))
+			splitted = splitted.substring(1);
+		MUST(available_towels.emplace_back(splitted));
+	}
+
+	ASSERT(fgets(buffer, sizeof(buffer), fp) && buffer[0] == '\n');
+
+	BAN::Vector<BAN::String> target_patterns;
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		usize len = strlen(buffer);
+		if (len == 0 || buffer[0] == '\n')
+			break;
+		ASSERT(buffer[len - 1] == '\n');
+		buffer[len - 1] = '\0';
+		MUST(target_patterns.emplace_back(BAN::StringView(buffer, len - 1)));
+	}
+
+	return ParseInputResult {
+		.available_towels = BAN::move(available_towels),
+		.target_patterns = BAN::move(target_patterns),
+	};
+}
+
+static bool recurse_part1(BAN::StringView target, const BAN::Vector<BAN::String>& available, usize index, BAN::HashSet<BAN::StringView>& not_possible)
+{
+	if (index >= target.size())
+		return true;
+	if (not_possible.contains(target.substring(index)))
+		return false;
+
+	for (const auto& towel : available)
+	{
+		if (!target.substring(index).starts_with(towel))
+			continue;
+		if (recurse_part1(target, available, index + towel.size(), not_possible))
+			return true;
+	}
+
+	MUST(not_possible.insert(target.substring(index)));
+
+	return false;
+}
+
+i64 part1(FILE* fp)
+{
+	auto [available, targets] = parse_input(fp);
+
+	BAN::HashSet<BAN::StringView> not_possible;
+
+	usize result = 0;
+	for (const auto& target : targets)
+		result += recurse_part1(target, available, 0, not_possible);
+	return result;
+}
+
+static u64 recurse_part2(BAN::StringView target, const BAN::Vector<BAN::String>& available, usize index, BAN::HashSet<BAN::StringView>& not_possible, BAN::HashMap<BAN::StringView, u64>& possible)
+{
+	if (index >= target.size())
+		return 1;
+	if (not_possible.contains(target.substring(index)))
+		return 0;
+
+	auto it = possible.find(target.substring(index));
+	if (it != possible.end())
+		return it->value;
+
+	usize ret = 0;
+	for (const auto& towel : available)
+	{
+		if (!target.substring(index).starts_with(towel))
+			continue;
+		ret += recurse_part2(target, available, index + towel.size(), not_possible, possible);
+	}
+
+	if (ret == 0)
+		MUST(not_possible.insert(target.substring(index)));
+	else
+		MUST(possible.insert_or_assign(target.substring(index), ret));
+
+	return ret;
+}
+
+i64 part2(FILE* fp)
+{
+	auto [available, targets] = parse_input(fp);
+
+	BAN::HashSet<BAN::StringView> not_possible;
+	BAN::HashMap<BAN::StringView, u64> possible;
+
+	u64 result = 0;
+	for (const auto& target : targets)
+		result += recurse_part2(target, available, 0, not_possible, possible);
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2024/day19_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);
+}