aoc2024: Implement day3 solution

userspace/aoc2024/CMakeLists.txt

@@ -1,6 +1,7 @@
 set(AOC2024_PROJECTS
 	day1
 	day2
+	day3
 	full
 )
 

userspace/aoc2024/day3/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2024_day3 ${SOURCES})
+banan_include_headers(aoc2024_day3 ban)
+banan_link_library(aoc2024_day3 libc)
+
+install(TARGETS aoc2024_day3 OPTIONAL)

userspace/aoc2024/day3/main.cpp

@@ -0,0 +1,152 @@
+#include <BAN/String.h>
+
+#include <inttypes.h>
+#include <stdio.h>
+#include <ctype.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 part1(FILE* fp)
+{
+	i64 result = 0;
+
+	BAN::String full_input;
+
+	{
+		char buffer[512];
+		while (fgets(buffer, sizeof(buffer), fp))
+			MUST(full_input.append(buffer));
+	}
+
+	result = 0;
+	for (size_t i = 0; i < full_input.size() - 4;)
+	{
+		if (!full_input.sv().substring(i).starts_with("mul("))
+		{
+			i++;
+			continue;
+		}
+
+		i += 4;
+		if (i >= full_input.size() || !isdigit(full_input[i]))
+			continue;
+
+		i64 lhs = atoll(&full_input[i]);
+		while (i < full_input.size() && isdigit(full_input[i]))
+			i++;
+
+		if (i >= full_input.size() || full_input[i] != ',')
+			continue;
+
+		i++;
+		if (i >= full_input.size() || !isdigit(full_input[i]))
+			continue;
+
+		int rhs = atoll(&full_input[i]);
+		while (i < full_input.size() && isdigit(full_input[i]))
+			i++;
+
+		if (i >= full_input.size() || full_input[i] != ')')
+			continue;
+
+		result += lhs * rhs;
+	}
+
+	return result;
+}
+
+i64 part2(FILE* fp)
+{
+	i64 result = 0;
+
+	BAN::String full_input;
+
+	{
+		char buffer[512];
+		while (fgets(buffer, sizeof(buffer), fp))
+			MUST(full_input.append(buffer));
+	}
+
+	bool state = true;
+
+	result = 0;
+	for (size_t i = 0; i < full_input.size();)
+	{
+		if (full_input.sv().substring(i).starts_with("do()"_sv))
+		{
+			state = true;
+			i += 4;
+			continue;
+		}
+
+		if (full_input.sv().substring(i).starts_with("don't()"_sv))
+		{
+			state = false;
+			i += 6;
+			continue;
+		}
+
+		if (state == false || !full_input.sv().substring(i).starts_with("mul("))
+		{
+			i++;
+			continue;
+		}
+
+		i += 4;
+		if (i >= full_input.size() || !isdigit(full_input[i]))
+			continue;
+
+		i64 lhs = atoll(&full_input[i]);
+		while (i < full_input.size() && isdigit(full_input[i]))
+			i++;
+
+		if (i >= full_input.size() || full_input[i] != ',')
+			continue;
+
+		i++;
+		if (i >= full_input.size() || !isdigit(full_input[i]))
+			continue;
+
+		int rhs = atoll(&full_input[i]);
+		while (i < full_input.size() && isdigit(full_input[i]))
+			i++;
+
+		if (i >= full_input.size() || full_input[i] != ')')
+			continue;
+
+		result += lhs * rhs;
+	}
+
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2024/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);
+}