AOC2023: Implement day15

userspace/aoc2023/CMakeLists.txt

@@ -17,6 +17,7 @@ set(AOC2023_PROJECTS
 	day12
 	day13
 	day14
+	day15
 )
 
 set(BANAN_AOC2023_BIN   ${BANAN_BIN}/aoc2023)

userspace/aoc2023/day15/CMakeLists.txt

@@ -0,0 +1,22 @@
+cmake_minimum_required(VERSION 3.26)
+
+project(aoc2023_day15 CXX)
+
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2023_day15 ${SOURCES})
+target_compile_options(aoc2023_day15 PUBLIC -O2 -g)
+target_link_libraries(aoc2023_day15 PUBLIC libc ban)
+
+add_dependencies(aoc2023_day15 libc-install ban-install)
+
+add_custom_target(aoc2023_day15-install
+	COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/aoc2023_day15 ${BANAN_AOC2023_BIN}/day15
+	DEPENDS aoc2023_day15
+	DEPENDS aoc2023_always
+)
+
+add_dependencies(aoc2023 aoc2023_day15)
+add_dependencies(aoc2023-install aoc2023_day15-install)

userspace/aoc2023/day15/main.cpp

@@ -0,0 +1,150 @@
+#include <BAN/Array.h>
+#include <BAN/LinkedList.h>
+#include <BAN/String.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;
+
+i64 parse_i64(BAN::StringView string)
+{
+	i64 result = 0;
+	for (char c : string)
+		result = (result * 10) + (c - '0');
+	return result;
+}
+
+BAN::Vector<BAN::StringView> parse_instructions(FILE* fp)
+{
+	static BAN::String line;
+
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		BAN::StringView buffer_sv(buffer);
+		MUST(line.append(buffer_sv));
+		if (buffer_sv.back() == '\n')
+		{
+			line.pop_back();
+			break;
+		}
+	}
+
+	return MUST(line.sv().split(','));
+}
+
+i64 calculate_hash(BAN::StringView string)
+{
+	i64 result = 0;
+	for (char c : string)
+		result = ((result + c) * 17) % 256;
+	return result;
+}
+
+i64 puzzle1(FILE* fp)
+{
+	auto instructions = parse_instructions(fp);
+
+	i64 result = 0;
+	for (auto insn : instructions)
+		result += calculate_hash(insn);
+	return result;
+}
+
+i64 puzzle2(FILE* fp)
+{
+	struct Entry
+	{
+		BAN::String label;
+		i64 focal_length;
+	};
+	using Box = BAN::LinkedList<Entry>;
+
+	auto instructions = parse_instructions(fp);
+
+	BAN::Array<Box, 256> boxes;
+
+	for (auto insn : instructions)
+	{
+		if (insn.back() == '-')
+		{
+			auto label = insn.substring(0, insn.size() - 1);
+			i64 hash = calculate_hash(label);
+
+			for (auto it = boxes[hash].begin(); it != boxes[hash].end(); it++)
+			{
+				if (it->label == label)
+				{
+					boxes[hash].remove(it);
+					break;
+				}
+			}
+		}
+		else
+		{
+			auto temp = MUST(insn.split('='));
+
+			auto label = temp[0];
+			auto focal_length = parse_i64(temp[1]);
+			i64 hash = calculate_hash(label);
+
+			bool found = false;
+			for (auto it = boxes[hash].begin(); it != boxes[hash].end(); it++)
+			{
+				if (it->label == label)
+				{
+					it->focal_length = focal_length;
+					found = true;
+					break;
+				}
+			}
+			if (!found)
+				MUST(boxes[hash].emplace_back(label, focal_length));
+		}
+	}
+
+	i64 result = 0;
+	for (size_t i = 0; i < boxes.size(); i++)
+	{
+		size_t slot = 0;
+		for (auto it = boxes[i].begin(); it != boxes[i].end(); it++, slot++)
+			result += (i + 1) * (slot + 1) * it->focal_length;
+	}
+
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2023/day15_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);
+}