aoc2025: Implement day10 solution

userspace/aoc2025/CMakeLists.txt

@@ -8,6 +8,7 @@ set(AOC2025_PROJECTS
 	day7
 	day8
 	day9
+	day10
 	full
 )
 

userspace/aoc2025/day10/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2025_day10 ${SOURCES})
+banan_include_headers(aoc2025_day10 ban)
+banan_link_library(aoc2025_day10 libc)
+
+install(TARGETS aoc2025_day10 OPTIONAL)

userspace/aoc2025/day10/main.cpp

@@ -0,0 +1,216 @@
+#include <BAN/String.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;
+
+struct Machine
+{
+	u32 indicator;
+	BAN::Vector<u32> buttons;
+	BAN::Vector<u32> joltages;
+};
+
+static BAN::Vector<Machine> parse_machines(FILE* fp)
+{
+	BAN::Vector<Machine> machines;
+
+	BAN::String line;
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		MUST(line.append(buffer));
+		if (line.back() != '\n')
+			continue;
+		if (line.front() != '[')
+			break;
+
+		Machine machine {};
+
+		size_t i = 1;
+		while (line[i] != ']')
+		{
+			if (line[i] == '#')
+				machine.indicator |= 1 << (i - 1);
+			i++;
+		}
+
+		i += 2;
+
+		while (line[i++] == '(')
+		{
+			u32 button = 0;
+
+			while (line[i] != ')')
+			{
+				if (line[i] == ',')
+					i++;
+
+				u32 index = 0;
+				while (isdigit(line[i]))
+					index = (index * 10) + (line[i++] - '0');
+
+				button |= 1 << index;
+			}
+
+			MUST(machine.buttons.push_back(button));
+
+			i += 2;
+		}
+
+		i--;
+
+		ASSERT(line[i] == '{');
+		while (line[i++] != '}')
+		{
+			u32 joltage = 0;
+			while (isdigit(line[i]))
+				joltage = (joltage * 10) + (line[i++] - '0');
+			MUST(machine.joltages.push_back(joltage));
+		}
+
+		MUST(machines.push_back(BAN::move(machine)));
+
+		line.clear();
+	}
+
+	return machines;
+}
+
+i64 part1(FILE* fp)
+{
+	static constexpr bool (*works_with_n_buttons)(const Machine&, size_t, size_t, u32) =
+		[](const Machine& machine, size_t buttons, size_t index, u32 state) -> bool
+		{
+			if (buttons == 0)
+				return state == machine.indicator;
+			for (size_t i = index; i < machine.buttons.size(); i++)
+				if (works_with_n_buttons(machine, buttons - 1, i + 1, state ^ machine.buttons[i]))
+					return true;
+			return false;
+		};
+
+	i64 result = 0;
+
+	auto machines = parse_machines(fp);
+	for (const auto& machine : machines)
+	{
+		for (size_t i = 1; i < machine.buttons.size(); i++)
+		{
+			if (!works_with_n_buttons(machine, i, 0, 0))
+				continue;
+			result += i;
+			break;
+		}
+	}
+
+	return result;
+}
+
+// based on https://www.reddit.com/r/adventofcode/comments/1pk87hl/2025_day_10_part_2_bifurcate_your_way_to_victory/
+
+static u32 minimum_presses(const BAN::Vector<BAN::Vector<u32>>& possible_indicators, const BAN::Vector<u32>& buttons, const BAN::Vector<u32>& joltages)
+{
+	bool all_zeroes = true;
+	for (u32 joltage : joltages)
+		if (joltage != 0)
+			all_zeroes = false;
+	if (all_zeroes)
+		return 0;
+
+	u32 indicator = 0;
+	for (size_t i = 0; i < joltages.size(); i++)
+		if (joltages[i] % 2)
+			indicator |= 1 << i;
+
+	u32 result = 1'000'000;
+
+	for (u32 button_mask : possible_indicators[indicator])
+	{
+		size_t button_count = 0;
+		BAN::Vector<u32> new_joltages = joltages;
+		for (size_t i = 0; i < buttons.size(); i++)
+		{
+			if (!(button_mask & (1 << i)))
+				continue;
+			button_count++;
+			for (size_t bit = 0; bit < new_joltages.size(); bit++)
+			{
+				if (!(buttons[i] & (1 << bit)))
+					continue;
+				if (new_joltages[bit] == 0)
+					goto unusable;
+				new_joltages[bit]--;
+			}
+		}
+
+		for (u32& joltage : new_joltages)
+			joltage /= 2;
+		result = BAN::Math::min<u32>(result, button_count + 2 * minimum_presses(possible_indicators, buttons, new_joltages));
+
+	unusable:
+		(void)0;
+	}
+
+	return result;
+}
+
+i64 part2(FILE* fp)
+{
+	i64 result = 0;
+
+	auto machines = parse_machines(fp);
+	for (const auto& machine : machines)
+	{
+		const size_t bits = machine.joltages.size();
+
+		BAN::Vector<BAN::Vector<u32>> possible_indicators;
+		MUST(possible_indicators.resize(1u << bits));
+		for (size_t button_mask = 0; button_mask < (1u << machine.buttons.size()); button_mask++)
+		{
+			u32 indicator = 0;
+			for (size_t button = 0; button < machine.buttons.size(); button++)
+				if (button_mask & (1 << button))
+					indicator ^= machine.buttons[button];
+			MUST(possible_indicators[indicator].push_back(button_mask));
+		}
+
+		result += minimum_presses(possible_indicators, machine.buttons, machine.joltages);
+	}
+
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2025/day10_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);
+}