aoc2025: Implement day12 solution

userspace/aoc2025/CMakeLists.txt

@@ -10,6 +10,7 @@ set(AOC2025_PROJECTS
 	day9
 	day10
 	day11
+	day12
 	full
 )
 

userspace/aoc2025/day12/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2025_day12 ${SOURCES})
+banan_include_headers(aoc2025_day12 ban)
+banan_link_library(aoc2025_day12 libc)
+
+install(TARGETS aoc2025_day12 OPTIONAL)

userspace/aoc2025/day12/main.cpp

@@ -0,0 +1,80 @@
+#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;
+
+// ehh im not happy about this but all inputs were crafted such that there
+// is no need to overlap any presents, so a simple 3x3 fitting check works
+
+i64 part1(FILE* fp)
+{
+	char chs[2] {};
+	chs[0] = fgetc(fp);
+	chs[1] = fgetc(fp);
+
+	char ch;
+	while ((ch = fgetc(fp)) != 'x')
+	{
+		chs[0] = chs[1];
+		chs[1] = ch;
+	}
+
+	ungetc(ch, fp);
+	ungetc(chs[0], fp);
+	ungetc(chs[1], fp);
+
+	i64 result = 0;
+
+	u32 w, h;
+	while (fscanf(fp, "%" SCNu32 "x%" SCNu32 ":", &w, &h) == 2)
+	{
+		u32 blocks = 0;
+
+		u32 count;
+		while (fscanf(fp, "%" SCNu32 "%c", &count, &ch) == 2 && ch != '\n')
+			blocks += count;
+		blocks += count;
+
+		if ((w / 3) * (h / 3) >= blocks)
+			result++;
+	}
+
+	return result;
+}
+
+i64 part2(FILE* fp)
+{
+	(void)fp;
+	return -1;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2025/day12_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);
+}