From cf9ba737f01c17a7e013ce09755e8450e823a35c Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Sat, 7 Dec 2024 07:34:21 +0200
Subject: [PATCH] aoc2024: Implement day7 solution

---
 userspace/aoc2024/CMakeLists.txt      |   1 +
 userspace/aoc2024/day7/CMakeLists.txt |   9 +++
 userspace/aoc2024/day7/main.cpp       | 106 ++++++++++++++++++++++++++
 3 files changed, 116 insertions(+)
 create mode 100644 userspace/aoc2024/day7/CMakeLists.txt
 create mode 100644 userspace/aoc2024/day7/main.cpp

diff --git a/userspace/aoc2024/CMakeLists.txt b/userspace/aoc2024/CMakeLists.txt
index 25b928e8a1..f480b0e3f4 100644
--- a/userspace/aoc2024/CMakeLists.txt
+++ b/userspace/aoc2024/CMakeLists.txt
@@ -5,6 +5,7 @@ set(AOC2024_PROJECTS
 	day4
 	day5
 	day6
+	day7
 	full
 )
 
diff --git a/userspace/aoc2024/day7/CMakeLists.txt b/userspace/aoc2024/day7/CMakeLists.txt
new file mode 100644
index 0000000000..adec774404
--- /dev/null
+++ b/userspace/aoc2024/day7/CMakeLists.txt
@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2024_day7 ${SOURCES})
+banan_link_library(aoc2024_day7 ban)
+banan_link_library(aoc2024_day7 libc)
+
+install(TARGETS aoc2024_day7 OPTIONAL)
diff --git a/userspace/aoc2024/day7/main.cpp b/userspace/aoc2024/day7/main.cpp
new file mode 100644
index 0000000000..9cf66b3a5a
--- /dev/null
+++ b/userspace/aoc2024/day7/main.cpp
@@ -0,0 +1,106 @@
+#include <BAN/StringView.h>
+#include <BAN/String.h>
+#include <BAN/Vector.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;
+
+bool check_if_valid(const BAN::Vector<u64>& vals, size_t idx, u64 curr, bool concat)
+{
+	// NOTE: This does not apply in general case, but puzzle input
+	//       does not contain zeros or negative numbers
+	if (curr > vals[0])
+		return false;
+
+	if (idx >= vals.size())
+		return curr == vals[0];
+
+	if (check_if_valid(vals, idx + 1, curr + vals[idx], concat))
+		return true;
+	if (check_if_valid(vals, idx + 1, curr * vals[idx], concat))
+		return true;
+
+	if (!concat)
+		return false;
+	u64 mult = 1;
+	while (mult <= vals[idx])
+		mult *= 10;
+	return check_if_valid(vals, idx + 1, curr * mult + vals[idx], concat);
+}
+
+i64 part1(FILE* fp)
+{
+	i64 result = 0;
+
+	char buffer[1024];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		auto strs = MUST(BAN::StringView(buffer).split(' '));
+		if (strs.empty())
+			break;
+
+		BAN::Vector<u64> vals;
+		for (auto str : strs)
+			MUST(vals.push_back(atoll(str.data())));
+
+		if (check_if_valid(vals, 2, vals[1], false))
+			result += vals[0];
+	}
+
+	return result;
+}
+
+i64 part2(FILE* fp)
+{
+	i64 result = 0;
+
+	char buffer[1024];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		auto strs = MUST(BAN::StringView(buffer).split(' '));
+		if (strs.empty())
+			break;
+
+		BAN::Vector<u64> vals;
+		for (auto str : strs)
+			MUST(vals.push_back(atoll(str.data())));
+
+		if (check_if_valid(vals, 2, vals[1], true))
+			result += vals[0];
+	}
+
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2024/day7_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);
+}