AOC2023: Implement day9

userspace/aoc2023/CMakeLists.txt

@@ -11,6 +11,7 @@ set(AOC2023_PROJECTS
 	day6
 	day7
 	day8
+	day9
 )
 
 set(BANAN_AOC2023_BIN   ${BANAN_BIN}/aoc2023)

userspace/aoc2023/day9/CMakeLists.txt

@@ -0,0 +1,22 @@
+cmake_minimum_required(VERSION 3.26)
+
+project(aoc2023_day9 CXX)
+
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2023_day9 ${SOURCES})
+target_compile_options(aoc2023_day9 PUBLIC -O2 -g)
+target_link_libraries(aoc2023_day9 PUBLIC libc ban)
+
+add_dependencies(aoc2023_day9 libc-install ban-install)
+
+add_custom_target(aoc2023_day9-install
+	COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/aoc2023_day9 ${BANAN_AOC2023_BIN}/day9
+	DEPENDS aoc2023_day9
+	DEPENDS aoc2023_always
+)
+
+add_dependencies(aoc2023 aoc2023_day9)
+add_dependencies(aoc2023-install aoc2023_day9-install)

userspace/aoc2023/day9/main.cpp

@@ -0,0 +1,148 @@
+#include <BAN/String.h>
+#include <BAN/Vector.h>
+
+#include <ctype.h>
+#include <stdio.h>
+#include <stdint.h>
+
+using i32 = int32_t;
+using i64 = int64_t;
+
+using u32 = uint32_t;
+using u64 = uint64_t;
+
+i64 parse_i64(BAN::StringView sv)
+{
+	bool negative = (!sv.empty() && sv.front() == '-');
+	if (negative)
+		sv = sv.substring(1);
+	
+	i64 result = 0;
+	for (char c : sv)
+	{
+		if (!isdigit(c))
+			break;
+		result = (result * 10) + (c - '0');
+	}
+	return negative ? -result : result;
+}
+
+i64 puzzle1(FILE* fp)
+{
+	i64 result = 0;
+
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		BAN::StringView line(buffer);
+
+		auto value_strs = MUST(line.split(' '));
+		if (value_strs.empty())
+			continue;
+
+		BAN::Vector<BAN::Vector<i64>> values;
+		MUST(values.emplace_back(value_strs.size() + 1, 0));
+		for (size_t i = 0; i < value_strs.size(); i++)
+			values.back()[i] = parse_i64(value_strs[i]);
+
+		bool all_zeroes = false;
+		while (!all_zeroes)
+		{
+			size_t last = values.size();
+			MUST(values.emplace_back(values.back().size() - 1, 0));
+
+			all_zeroes = true;
+			for (size_t i = 0; i < values.back().size() - 1; i++)
+			{
+				i64 lhs = values[last - 1][i + 0];
+				i64 rhs = values[last - 1][i + 1];
+				values[last][i] = rhs - lhs;
+				if (values[last][i] != 0)
+					all_zeroes = false;
+			}
+		}
+
+		for (size_t i = values.size() - 1; i > 0; i--)
+		{
+			const size_t len = values[i].size();
+			i64 lhs = values[i - 1][len - 1];
+			i64 res = values[i][len - 1];
+			values[i - 1][len - 0] = res + lhs;
+		}
+
+		result += values.front().back();
+	}
+
+	return result;
+}
+
+i64 puzzle2(FILE* fp)
+{
+	i64 result = 0;
+
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		BAN::StringView line(buffer);
+
+		auto value_strs = MUST(line.split(' '));
+		if (value_strs.empty())
+			continue;
+
+		BAN::Vector<BAN::Vector<i64>> values;
+		MUST(values.emplace_back(value_strs.size() + 1, 0));
+		for (size_t i = 0; i < value_strs.size(); i++)
+			values.back()[i + 1] = parse_i64(value_strs[i]);
+
+		bool all_zeroes = false;
+		while (!all_zeroes)
+		{
+			size_t last = values.size();
+			MUST(values.emplace_back(values.back().size() - 1, 0));
+
+			all_zeroes = true;
+			for (size_t i = 1; i < values.back().size(); i++)
+			{
+				i64 lhs = values[last - 1][i + 0];
+				i64 rhs = values[last - 1][i + 1];
+				values[last][i] = rhs - lhs;
+				if (values[last][i] != 0)
+					all_zeroes = false;
+			}
+		}
+
+		for (size_t i = values.size() - 1; i > 0; i--)
+		{
+			i64 rhs = values[i - 1][1];
+			i64 res = values[i][0];
+			values[i - 1][0] = rhs - res;
+		}
+
+		result += values.front().front();
+	}
+
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2023/day9_input.txt";
+
+	if (argc >= 2)
+		file_path = argv[1];
+
+	FILE* fp = fopen(file_path, "r");
+	if (fp == nullptr)
+	{
+		perror("fopen");
+		return 1;
+	}
+
+	printf("puzzle1: %lld\n", puzzle1(fp));
+
+	fseek(fp, 0, SEEK_SET);
+
+	printf("puzzle2: %lld\n", puzzle2(fp));
+
+	fclose(fp);
+}