diff --git a/userspace/aoc2023/CMakeLists.txt b/userspace/aoc2023/CMakeLists.txt
index f18fb059..f302eb00 100644
--- a/userspace/aoc2023/CMakeLists.txt
+++ b/userspace/aoc2023/CMakeLists.txt
@@ -14,6 +14,7 @@ set(AOC2023_PROJECTS
 	day9
 	day10
 	day11
+	day12
 )
 
 set(BANAN_AOC2023_BIN   ${BANAN_BIN}/aoc2023)
diff --git a/userspace/aoc2023/day12/CMakeLists.txt b/userspace/aoc2023/day12/CMakeLists.txt
new file mode 100644
index 00000000..2b3b1705
--- /dev/null
+++ b/userspace/aoc2023/day12/CMakeLists.txt
@@ -0,0 +1,22 @@
+cmake_minimum_required(VERSION 3.26)
+
+project(aoc2023_day12 CXX)
+
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2023_day12 ${SOURCES})
+target_compile_options(aoc2023_day12 PUBLIC -O2 -g)
+target_link_libraries(aoc2023_day12 PUBLIC libc ban)
+
+add_dependencies(aoc2023_day12 libc-install ban-install)
+
+add_custom_target(aoc2023_day12-install
+	COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/aoc2023_day12 ${BANAN_AOC2023_BIN}/day12
+	DEPENDS aoc2023_day12
+	DEPENDS aoc2023_always
+)
+
+add_dependencies(aoc2023 aoc2023_day12)
+add_dependencies(aoc2023-install aoc2023_day12-install)
diff --git a/userspace/aoc2023/day12/main.cpp b/userspace/aoc2023/day12/main.cpp
new file mode 100644
index 00000000..3632f905
--- /dev/null
+++ b/userspace/aoc2023/day12/main.cpp
@@ -0,0 +1,166 @@
+#include <BAN/HashMap.h>
+#include <BAN/String.h>
+#include <BAN/Swap.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;
+
+u64 parse_u64(BAN::StringView str)
+{
+	u64 result = 0;
+	for (char c : str)
+		if (isdigit(c))
+			result = (result * 10) + (c - '0');
+	return result;
+}
+
+static BAN::HashMap<BAN::String, i64> s_cache;
+
+BAN::String build_cache_key(BAN::StringView record, BAN::Span<u64> groups)
+{
+	BAN::String cache_key;
+	MUST(cache_key.append(record));
+	for (u64 group : groups)
+		MUST(cache_key.append(BAN::String::formatted(" {}", group)));
+	return cache_key;
+}
+
+i64 count_possibilities(BAN::StringView record, BAN::Span<u64> groups)
+{
+	if (groups.empty())
+		return !record.contains('#');
+	if (record.empty())
+		return 0;
+
+	auto cache_key = build_cache_key(record, groups);
+	if (s_cache.contains(cache_key))
+		return s_cache[cache_key];
+
+	i64 result = 0;
+
+	for (size_t i = 0; i + groups[0] <= record.size(); i++)
+	{
+		bool valid = true;
+		
+		if (record.substring(i, groups[0]).contains('.'))
+			valid = false;
+
+		if (i + groups[0] < record.size() && record[i + groups[0]] == '#')
+			valid = false;
+
+		if (valid)
+		{
+			auto next_record = record.substring(i + groups[0]);
+			if (!next_record.empty())
+				next_record = next_record.substring(1);
+			result += count_possibilities(next_record, groups.slice(1));
+		}
+
+		if (record[i] == '#')
+			break;
+	}
+
+	//printf("inserting... "); fflush(stdout);
+	MUST(s_cache.insert(cache_key, result));
+	//printf("done\n");
+
+	return result;
+}
+
+i64 puzzle1(FILE* fp)
+{
+	i64 result = 0;
+
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		BAN::StringView line(buffer);
+		if (line.back() == '\n')
+			line = line.substring(0, line.size() - 1);
+		if (line.size() < 3)
+			continue;
+		
+		auto parts = MUST(line.split(' '));
+
+		auto record = parts[0];
+
+		auto continuous_strs = MUST(parts[1].split(','));
+		BAN::Vector<u64> continuous(continuous_strs.size());
+		for (size_t i = 0; i < continuous.size(); i++)
+			continuous[i] = parse_u64(continuous_strs[i]);
+
+		result += count_possibilities(record, continuous.span());
+	}
+
+	return result;
+}
+
+i64 puzzle2(FILE* fp)
+{
+	i64 result = 0;
+
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		BAN::StringView line(buffer);
+		if (line.back() == '\n')
+			line = line.substring(0, line.size() - 1);
+		if (line.size() < 3)
+			continue;
+		
+		auto parts = MUST(line.split(' '));
+
+		BAN::String record;
+		MUST(record.reserve(parts[0].size() + 4));
+		for (size_t i = 0; i < 5; i++)
+		{
+			if (i > 0)
+				MUST(record.push_back('?'));
+			MUST(record.append(parts[0]));
+		}
+
+		auto continuous_strs = MUST(parts[1].split(','));
+		BAN::Vector<u64> continuous(5 * continuous_strs.size());
+		for (size_t i = 0; i < continuous.size(); i++)
+			continuous[i] = parse_u64(continuous_strs[i % continuous_strs.size()]);
+
+		result += count_possibilities(record, continuous.span());
+	}
+
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2023/day12_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);
+}