aoc2024: implement day1 solution

userspace/aoc2024/CMakeLists.txt

@@ -1,4 +1,5 @@
 set(AOC2024_PROJECTS
+	day1
 	full
 )
 

userspace/aoc2024/day1/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2024_day1 ${SOURCES})
+banan_include_headers(aoc2024_day1 ban)
+banan_link_library(aoc2024_day1 libc)
+
+install(TARGETS aoc2024_day1 OPTIONAL)

userspace/aoc2024/day1/main.cpp

@@ -0,0 +1,101 @@
+#include <BAN/HashMap.h>
+#include <BAN/Vector.h>
+#include <BAN/Sort.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 part1(FILE* fp)
+{
+	BAN::Vector<i64> lhs;
+	BAN::Vector<i64> rhs;
+
+	for (;;) {
+		i64 l, r;
+		if (fscanf(fp, "%" SCNd64 " %" SCNd64 "\n", &l, &r) != 2)
+			break;
+		MUST(lhs.push_back(l));
+		MUST(rhs.push_back(r));
+	}
+
+	BAN::sort::sort(lhs.begin(), lhs.end());
+	BAN::sort::sort(rhs.begin(), rhs.end());
+
+	i64 result = 0;
+	for (size_t i = 0; i < lhs.size(); i++)
+		result += BAN::Math::abs(lhs[i] - rhs[i]);
+
+	return result;
+}
+
+i64 part2(FILE* fp)
+{
+	BAN::HashMap<i64, i64> lhs;
+	BAN::HashMap<i64, i64> rhs;
+
+	for (;;) {
+		i64 l, r;
+		if (fscanf(fp, "%" SCNd64 " %" SCNd64 "\n", &l, &r) != 2)
+			break;
+
+		{
+			auto it = lhs.find(l);
+			if (it == lhs.end())
+				MUST(lhs.insert(l, 1));
+			else
+				it->value++;
+		}
+
+		{
+			auto it = rhs.find(r);
+			if (it == rhs.end())
+				MUST(rhs.insert(r, 1));
+			else
+				it->value++;
+		}
+	}
+
+	i64 result = 0;
+
+	for (auto [id, count] : lhs) {
+		auto it = rhs.find(id);
+		if (it == rhs.end())
+			continue;
+		result += id * count * it->value;
+	}
+
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2024/day1_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);
+}