banan-os/userspace/aoc2023/day21/main.cpp

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2023-12-24 14:58:21 +02:00
#include <BAN/Vector.h>
#include <BAN/HashSet.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;
enum class Tile { Free, Rock };
struct Position
{
i64 x;
i64 y;
Position operator+(const Position& other) const
{
return {
.x = x + other.x,
.y = y + other.y
};
}
bool operator==(const Position& other) const
{
return x == other.x && y == other.y;
}
};
namespace BAN
{
template<>
struct hash<Position>
{
hash_t operator()(const Position& position) const
{
return hash<u64>()(((u64)position.x << 32) | (u64)position.y);
}
};
}
struct Garden
{
Position start;
BAN::Vector<BAN::Vector<Tile>> tiles;
};
Garden parse_garden(FILE* fp)
{
Garden garden;
i64 row = 0;
char buffer[256];
while (fgets(buffer, sizeof(buffer), fp))
{
BAN::StringView line(buffer);
ASSERT(line.back() == '\n');
line = line.substring(0, line.size() - 1);
if (line.empty())
break;
MUST(garden.tiles.emplace_back(line.size(), Tile::Free));
for (size_t i = 0; i < line.size(); i++)
{
if (line[i] == '#')
garden.tiles.back()[i] = Tile::Rock;
if (line[i] == 'S')
garden.start = { .x = (i64)i, .y = row };
}
row++;
}
return garden;
}
i64 puzzle1(FILE* fp)
{
auto garden = parse_garden(fp);
BAN::HashSetUnstable<Position> visited, reachable, pending;
MUST(pending.insert(garden.start));
for (i32 i = 0; i <= 64; i++)
{
auto temp = BAN::move(pending);
pending = BAN::HashSetUnstable<Position>();
while (!temp.empty())
{
auto position = *temp.begin();
temp.remove(position);
MUST(visited.insert(position));
if (i % 2 == 0)
MUST(reachable.insert(position));
Position offsets[4] { { -1, 0 }, { 1, 0 }, { 0, -1 }, { 0, 1 } };
for (i32 j = 0; j < 4; j++)
{
auto next = position + offsets[j];
if (next.y < 0 || next.y >= (i64)garden.tiles.size())
continue;
if (next.x < 0 || next.x >= (i64)garden.tiles[0].size())
continue;
if (garden.tiles[next.y][next.x] == Tile::Rock)
continue;
if (visited.contains(next))
continue;
MUST(pending.insert(next));
}
}
}
return reachable.size();
}
i64 puzzle2(FILE* fp)
{
(void)fp;
return -1;
}
int main(int argc, char** argv)
{
const char* file_path = "/usr/share/aoc2023/day21_input.txt";
if (argc >= 2)
file_path = argv[1];
FILE* fp = fopen(file_path, "r");
if (fp == nullptr)
{
perror("fopen");
return 1;
}
printf("puzzle1: %" PRId64 "\n", puzzle1(fp));
fseek(fp, 0, SEEK_SET);
printf("puzzle2: %" PRId64 "\n", puzzle2(fp));
fclose(fp);
}