banan-os/userspace/aoc2023/day18/main.cpp

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2023-12-23 18:47:21 +02:00
#include <BAN/HashSet.h>
#include <BAN/StringView.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;
struct Position
{
i32 x;
i32 y;
bool operator==(const Position& other) const
{
return x == other.x && y == other.y;
}
Position& operator+=(const Position& other)
{
x += other.x;
y += other.y;
return *this;
}
Position operator+(const Position& other) const
{
Position temp = *this;
temp += other;
return temp;
}
};
struct PositionHash
{
BAN::hash_t operator()(const Position& position) const
{
return BAN::u64_hash(((u64)position.x << 32) | (u64)position.y);
}
};
enum Direction { North, West, South, East };
static constexpr Direction char_to_dir(char c)
{
if (c == 'U')
return Direction::North;
if (c == 'D')
return Direction::South;
if (c == 'L')
return Direction::West;
if (c == 'R')
return Direction::East;
ASSERT_NOT_REACHED();
}
static constexpr Position s_dir_offset[] {
{ .x = 0, .y = -1 },
{ .x = -1, .y = 0 },
{ .x = 0, .y = 1 },
{ .x = 1, .y = 0 },
};
i64 solve_general(FILE* fp, auto parse_dir, auto parse_count)
{
BAN::HashSetUnstable<Position, PositionHash> path;
BAN::HashSetUnstable<Position, PositionHash> lpath;
BAN::HashSetUnstable<Position, PositionHash> rpath;
Position current_pos { 0, 0 };
MUST(path.insert(current_pos));
char buffer[128];
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;
auto dir = parse_dir(line);
i64 count = parse_count(line);
Position loff, roff;
switch (dir)
{
case Direction::North:
loff = s_dir_offset[Direction::West];
roff = s_dir_offset[Direction::East];
break;
case Direction::South:
loff = s_dir_offset[Direction::East];
roff = s_dir_offset[Direction::West];
break;
case Direction::East:
loff = s_dir_offset[Direction::North];
roff = s_dir_offset[Direction::South];
break;
case Direction::West:
loff = s_dir_offset[Direction::South];
roff = s_dir_offset[Direction::North];
break;
}
for (i64 i = 0; i < count; i++)
{
current_pos += s_dir_offset[dir];
MUST(path.insert(current_pos));
MUST(lpath.insert(current_pos + loff));
MUST(rpath.insert(current_pos + roff));
}
}
for (auto position : path)
{
if (lpath.contains(position))
lpath.remove(position);
if (rpath.contains(position))
rpath.remove(position);
}
auto find_min_and_remove_duplicates =
[](auto& source, auto& destination, i32& minimum)
{
for (auto it = source.begin(); it != source.end();)
{
if (!destination.contains(*it))
{
minimum = BAN::Math::min(minimum, it->x);
it++;
}
else
{
source.remove(*it);
destination.remove(*it);
it = source.begin();
}
}
};
i32 lmin_x = INT32_MAX;
find_min_and_remove_duplicates(lpath, rpath, lmin_x);
i32 rmin_x = INT32_MAX;
find_min_and_remove_duplicates(rpath, lpath, rmin_x);
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ASSERT(lmin_x != rmin_x);
auto& expand = (lmin_x < rmin_x) ? rpath : lpath;
BAN::HashSetUnstable<Position, PositionHash> visited;
BAN::HashSetUnstable<Position, PositionHash> inner_area;
while (!expand.empty())
{
auto position = *expand.begin();
expand.remove(position);
MUST(inner_area.insert(position));
MUST(visited.insert(position));
for (i8 dir = 0; dir < 4; dir++)
{
auto next = position + s_dir_offset[dir];
if (visited.contains(next) || path.contains(next))
continue;
MUST(expand.insert(next));
MUST(visited.insert(next));
}
}
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return path.size() + inner_area.size();
}
i64 puzzle1(FILE* fp)
{
auto parse_dir =
[](auto line)
{
if (line[0] == 'U')
return Direction::North;
if (line[0] == 'D')
return Direction::South;
if (line[0] == 'L')
return Direction::West;
if (line[0] == 'R')
return Direction::East;
ASSERT_NOT_REACHED();
};
auto parse_count =
[](auto line)
{
i64 result = 0;
for (size_t i = 2; i < line.size() && isdigit(line[i]); i++)
result = (result * 10) + (line[i] - '0');
return result;
};
return solve_general(fp, parse_dir, parse_count);
}
i64 puzzle2(FILE* fp)
{
//(#7a21e3)
auto parse_dir =
[](auto line)
{
line = line.substring(*line.find('('));
if (line[7] == '0')
return Direction::East;
if (line[7] == '1')
return Direction::South;
if (line[7] == '2')
return Direction::West;
if (line[7] == '3')
return Direction::North;
ASSERT_NOT_REACHED();
};
auto parse_count =
[](auto line)
{
line = line.substring(*line.find('('));
i64 result = 0;
for (size_t i = 2; i < 7; i++)
result = (result * 16) + ((isdigit(line[i])) ? (line[i] - '0') : (tolower(line[i] - 'a' + 10)));
return result;
};
return solve_general(fp, parse_dir, parse_count);
}
int main(int argc, char** argv)
{
const char* file_path = "/usr/share/aoc2023/day18_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);
}