From ddfb591094f62fdd8e1c105a3525f2ece954154b Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Fri, 12 Dec 2025 04:20:06 +0200
Subject: [PATCH] aoc2025: Implement day3 solution

---
 userspace/aoc2025/CMakeLists.txt      |  1 +
 userspace/aoc2025/day3/CMakeLists.txt |  9 +++
 userspace/aoc2025/day3/main.cpp       | 90 +++++++++++++++++++++++++++
 3 files changed, 100 insertions(+)
 create mode 100644 userspace/aoc2025/day3/CMakeLists.txt
 create mode 100644 userspace/aoc2025/day3/main.cpp

diff --git a/userspace/aoc2025/CMakeLists.txt b/userspace/aoc2025/CMakeLists.txt
index 8b32544d..5a4e4368 100644
--- a/userspace/aoc2025/CMakeLists.txt
+++ b/userspace/aoc2025/CMakeLists.txt
@@ -1,6 +1,7 @@
 set(AOC2025_PROJECTS
 	day1
 	day2
+	day3
 	full
 )
 
diff --git a/userspace/aoc2025/day3/CMakeLists.txt b/userspace/aoc2025/day3/CMakeLists.txt
new file mode 100644
index 00000000..fe35fb5d
--- /dev/null
+++ b/userspace/aoc2025/day3/CMakeLists.txt
@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2025_day3 ${SOURCES})
+banan_include_headers(aoc2025_day3 ban)
+banan_link_library(aoc2025_day3 libc)
+
+install(TARGETS aoc2025_day3 OPTIONAL)
diff --git a/userspace/aoc2025/day3/main.cpp b/userspace/aoc2025/day3/main.cpp
new file mode 100644
index 00000000..6f58e963
--- /dev/null
+++ b/userspace/aoc2025/day3/main.cpp
@@ -0,0 +1,90 @@
+#include <BAN/Math.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 get_max_joltage(const char* line, size_t batteries)
+{
+	size_t line_len = 0;
+	while (isdigit(line[line_len]))
+		line_len++;
+	if (line_len < batteries)
+		return 0;
+
+	i64 result = 0;
+
+	size_t max_i = -1;
+	for (size_t battery = 0; battery < batteries; battery++)
+	{
+		i32 value = 0;
+		for (size_t i = max_i + 1; i < line_len - batteries + battery + 1; i++)
+		{
+			if (line[i] - '0' <= value)
+				continue;
+			value = line[i] - '0';
+			max_i = i;
+
+			if (value == 9)
+				break;
+		}
+		result = (result * 10) + value;
+	}
+
+	return result;
+}
+
+i64 part1(FILE* fp)
+{
+	i64 result = 0;
+
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+		result += get_max_joltage(buffer, 2);
+
+	return result;
+}
+
+i64 part2(FILE* fp)
+{
+	i64 result = 0;
+
+	char buffer[128];
+	while (fgets(buffer, sizeof(buffer), fp))
+		result += get_max_joltage(buffer, 12);
+
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2025/day3_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);
+}