advent-of-code/2022/d15/ex1/ex1.py

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2022-12-15 11:14:33 +01:00
#!/usr/bin/env python
import dataclasses
import functools
import sys
from collections.abc import Iterable
from typing import NamedTuple, Optional
class Point(NamedTuple):
x: int
y: int
@classmethod
def from_input(cls, input: str) -> "Point":
assert input.startswith("x=") # Sanity check
x, y = input.split(", ")
return cls(int(x.split("=")[-1]), int(y.split("=")[-1]))
class Interval(NamedTuple):
start: int
end: int
def as_set(self) -> set[int]:
return set(range(self.start, self.end + 1))
def merge_intervals(intervals: Iterable[Interval]) -> list[Interval]:
intervals = sorted(intervals)
res = [intervals[0]]
for candidate in intervals[1:]:
# Range is inclusive in both end, so add 1 to end in case of near miss
if (res[-1].end + 1) >= candidate.start:
new_end = max(res[-1].end, candidate.end)
res[-1] = Interval(res[-1].start, new_end)
else:
res.append(candidate)
return res
def distance(a: Point, b: Point) -> int:
return abs(a.x - b.x) + abs(a.y - b.y)
@dataclasses.dataclass
class SensorData:
pos: Point
beacon: Point
@classmethod
def from_input(cls, input: str) -> "SensorData":
assert input.startswith("Sensor at x=") # Sanity check
mid = input.index(":")
sensor, beacon = input[:mid], input[mid:]
return cls(
Point.from_input(sensor[sensor.index("x") :]),
Point.from_input(beacon[beacon.index("x") :]),
)
@functools.cached_property
def safe_range(self) -> int:
return distance(self.pos, self.beacon)
def scan_row(self, row: int) -> Optional[Interval]:
distance = abs(row - self.pos.y)
dx = self.safe_range - distance
if dx < 0:
return None
return Interval(self.pos.x - dx, self.pos.x + dx)
def solve(input: list[str]) -> int:
def points_without_sos(data: list[SensorData], row: int) -> list[Interval]:
intervals = (d.scan_row(row) for d in data)
return merge_intervals(i for i in intervals if i is not None)
data = [SensorData.from_input(line) for line in input]
beacons = {d.beacon for d in data}
ROW = 2_000_000
intervals = points_without_sos(data, ROW)
return len(
set.union(*(i.as_set() for i in intervals))
- {b.x for b in beacons if b.y == ROW}
)
def main() -> None:
input = sys.stdin.read().splitlines()
print(solve(input))
if __name__ == "__main__":
main()