From 41f897408007aec2139fa9dbf2f0723185392ada Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Mon, 4 Dec 2023 17:51:27 +0200
Subject: [PATCH] AOC2023: implement day4

---
 userspace/aoc2023/CMakeLists.txt      |  1 +
 userspace/aoc2023/day4/CMakeLists.txt | 22 +++++++
 userspace/aoc2023/day4/main.cpp       | 92 +++++++++++++++++++++++++++
 3 files changed, 115 insertions(+)
 create mode 100644 userspace/aoc2023/day4/CMakeLists.txt
 create mode 100644 userspace/aoc2023/day4/main.cpp

diff --git a/userspace/aoc2023/CMakeLists.txt b/userspace/aoc2023/CMakeLists.txt
index 8d97095c..d21ce7be 100644
--- a/userspace/aoc2023/CMakeLists.txt
+++ b/userspace/aoc2023/CMakeLists.txt
@@ -6,6 +6,7 @@ set(AOC2023_PROJECTS
 	day1
 	day2
 	day3
+	day4
 )
 
 set(BANAN_AOC2023_BIN   ${BANAN_BIN}/aoc2023)
diff --git a/userspace/aoc2023/day4/CMakeLists.txt b/userspace/aoc2023/day4/CMakeLists.txt
new file mode 100644
index 00000000..f934e8a1
--- /dev/null
+++ b/userspace/aoc2023/day4/CMakeLists.txt
@@ -0,0 +1,22 @@
+cmake_minimum_required(VERSION 3.26)
+
+project(aoc2023_day4 CXX)
+
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2023_day4 ${SOURCES})
+target_compile_options(aoc2023_day4 PUBLIC -O2 -g)
+target_link_libraries(aoc2023_day4 PUBLIC libc ban)
+
+add_dependencies(aoc2023_day4 libc-install ban-install)
+
+add_custom_target(aoc2023_day4-install
+	COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/aoc2023_day4 ${BANAN_AOC2023_BIN}/day4
+	DEPENDS aoc2023_day4
+	DEPENDS aoc2023_always
+)
+
+add_dependencies(aoc2023 aoc2023_day4)
+add_dependencies(aoc2023-install aoc2023_day4-install)
diff --git a/userspace/aoc2023/day4/main.cpp b/userspace/aoc2023/day4/main.cpp
new file mode 100644
index 00000000..1bc4ed36
--- /dev/null
+++ b/userspace/aoc2023/day4/main.cpp
@@ -0,0 +1,92 @@
+#include <BAN/Vector.h>
+#include <BAN/String.h>
+#include <BAN/StringView.h>
+
+#include <stdio.h>
+#include <string.h>
+
+static int matching_numbers(BAN::StringView line)
+{
+	ASSERT(line.size() == 117);
+	line = line.substring(0, line.size() - 1);
+
+	auto winning_numbers = MUST(line.substring(10, 29).split(' '));
+	auto your_numbers = MUST(line.substring(42).split(' '));
+
+	int matching = 0;
+	for (auto number : your_numbers)
+		if (winning_numbers.contains(number))
+			matching++;
+
+	return matching;
+}
+
+int puzzle1(FILE* fp)
+{
+	int result = 0;
+
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		if (strncmp(buffer, "Card", 4))
+			continue;
+
+		int matching = matching_numbers(buffer);
+		int points = !!matching;
+		for (int i = 1; i < matching; i++)
+			points *= 2;
+		result += points;
+	}
+
+	return result;
+}
+
+int puzzle2(FILE* fp)
+{
+	struct Card
+	{
+		BAN::String line;
+		int count;
+	};
+
+	BAN::Vector<Card> cards;
+
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+		if (strncmp(buffer, "Card", 4) == 0)
+			MUST(cards.emplace_back(BAN::StringView(buffer), 1));
+
+	int result = 0;
+	for (size_t i = 0; i < cards.size(); i++)
+	{
+		int matching = matching_numbers(cards[i].line);
+		for (int j = 0; j < matching; j++)
+			cards[i + j + 1].count += cards[i].count;
+		result += cards[i].count;
+	}
+
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2023/day4_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);
+}