AOC2023: implement day3

Solution to second puzzle is not optimal, it definately should be
O(1) space, but I didn't want to think about it.

userspace/aoc2023/CMakeLists.txt

@@ -4,6 +4,8 @@ project(aoc2023 CXX)
 
 set(AOC2023_PROJECTS
 	day1
+	day2
+	day3
 )
 
 set(BANAN_AOC2023_BIN   ${BANAN_BIN}/aoc2023)

userspace/aoc2023/day3/CMakeLists.txt

@@ -0,0 +1,22 @@
+cmake_minimum_required(VERSION 3.26)
+
+project(aoc2023_day3 CXX)
+
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2023_day3 ${SOURCES})
+target_compile_options(aoc2023_day3 PUBLIC -O2 -g)
+target_link_libraries(aoc2023_day3 PUBLIC libc ban)
+
+add_dependencies(aoc2023_day3 libc-install ban-install)
+
+add_custom_target(aoc2023_day3-install
+	COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/aoc2023_day3 ${BANAN_AOC2023_BIN}/day3
+	DEPENDS aoc2023_day3
+	DEPENDS aoc2023_always
+)
+
+add_dependencies(aoc2023 aoc2023_day3)
+add_dependencies(aoc2023-install aoc2023_day3-install)

userspace/aoc2023/day3/main.cpp

@@ -0,0 +1,179 @@
+#include <BAN/HashMap.h>
+#include <BAN/String.h>
+#include <BAN/Vector.h>
+
+#include <ctype.h>
+#include <stdio.h>
+#include <string.h>
+
+int puzzle1(FILE* fp)
+{
+	using BAN::Vector, BAN::String;
+
+	Vector<String> lines;
+
+	char buffer[256];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		buffer[strlen(buffer) - 1] = '\0';
+		MUST(lines.emplace_back(buffer));
+	}	
+
+	int result = 0;
+
+	for (ssize_t y = 0; y < lines.size(); y++)
+	{
+		for (ssize_t x = 0; x < lines[y].size(); x++)
+		{			
+			if (!isdigit(lines[y][x]))
+				continue;
+
+			bool should_add = false;
+
+			for (ssize_t y_off = -1; y_off <= 1; y_off++)
+			{
+				if (y + y_off < 0)
+					continue;
+				if (y + y_off >= lines.size())
+					break;
+
+				for (ssize_t x_off = -1;; x_off++)
+				{
+					if (x + x_off < 0)
+						continue;
+					if (x + x_off >= lines[y + y_off].size())
+						break;
+					if (x_off > 0 && !isdigit(lines[y][x + x_off - 1]))
+						break;
+
+					char c = lines[y + y_off][x + x_off];
+					if (!isdigit(c) && c != '.')
+					{
+						should_add = true;
+						break;
+					}
+				}	
+
+				if (should_add)
+					break;
+			}
+
+			int number = 0;
+			for (; x < lines[y].size(); x++)
+			{
+				if (!isdigit(lines[y][x]))
+				{
+					x--;
+					break;
+				}
+				number = (number * 10) + (lines[y][x] - '0');
+			}
+
+			if (should_add)
+				result += number;
+		}
+	}
+
+	return result;
+}
+
+int puzzle2(FILE* fp)
+{
+	using BAN::Vector, BAN::String, BAN::HashMap;
+
+	Vector<String> lines;
+
+	char buffer[256];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		buffer[strlen(buffer) - 1] = '\0';
+		MUST(lines.emplace_back(buffer));
+	}	
+
+	// Didn't want to think about O(1) space, this is much simpler.
+	// Map numbers next to '*' to asterisk's coordinates.
+	HashMap<uint32_t, Vector<int>> gears;
+
+	for (ssize_t y = 0; y < lines.size(); y++)
+	{
+		for (ssize_t x = 0; x < lines[y].size(); x++)
+		{
+			if (!isdigit(lines[y][x]))
+				continue;
+
+			int number = 0;
+			for (int i = 0; x + i < lines[y].size(); i++)
+			{
+				if (!isdigit(lines[y][x + i]))
+					break;
+				number = (number * 10) + (lines[y][x + i] - '0');
+			}
+
+			for (ssize_t y_off = -1; y_off <= 1; y_off++)
+			{
+				if (y + y_off < 0)
+					continue;
+				if (y + y_off >= lines.size())
+					break;
+
+				for (ssize_t x_off = -1;; x_off++)
+				{
+					if (x + x_off < 0)
+						continue;
+					if (x + x_off >= lines[y + y_off].size())
+						break;
+					if (x_off > 0 && !isdigit(lines[y][x + x_off - 1]))
+						break;
+
+					if (lines[y + y_off][x + x_off] == '*')
+					{
+						uint32_t index = (y + y_off) << 16 | (x + x_off);
+						if (!gears.contains(index))
+							MUST(gears.insert(index, {}));
+						MUST(gears[index].push_back(number));
+					}
+				}
+			}
+
+			for (; x < lines[y].size(); x++)
+			{
+				if (isdigit(lines[y][x]))
+					continue;
+				x--;
+				break;
+			}
+		}
+	}
+
+	int result = 0;
+	for (auto& [_, nums] : gears)
+	{
+		if (nums.size() != 2)
+			continue;
+		result += nums[0] * nums[1];
+	}
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2023/day3_input.txt";
+
+	if (argc >= 2)
+		file_path = argv[1];
+
+	FILE* fp = fopen(file_path, "r");
+	if (fp == nullptr)
+	{
+		perror("fopen");
+		return 1;
+	}
+
+	printf("puzzle1: %d\n", puzzle1(fp));
+
+	fseek(fp, 0, SEEK_SET);
+
+	printf("puzzle2: %d\n", puzzle2(fp));
+
+	fclose(fp);
+}