Advent of code 2024 day 12

day12.py

import fileinput
from itertools import product
import networkx as nx  # type: ignore
import shapely  # type: ignore

data = [line.strip() for line in fileinput.input()]
Y, X = len(data), len(data[0])

g = nx.Graph()
sides = {}
for y, x in product(range(Y), range(X)):
    pos = (y, x)
    val = data[y][x]
    sides[pos] = {pos}
    g.add_node(pos, name=val)
    for yn, xn in ((y - 1, x), (y + 1, x), (y, x - 1), (y, x + 1)):
        if 0 <= yn < Y and 0 <= xn < X and data[yn][xn] == val:
            g.add_edge(pos, (yn, xn), name=val)
            sides[pos].add((yn, xn))

def calcp1_perim(path: set[tuple[int, int]]) -> int:
    return sum((5 - len(sides[pos])) for pos in path)

def length(line: shapely.LineString) -> int:
    return len(shapely.simplify(line, 0.1).coords) - 1

def calcp2_perim(path: set[tuple[int, int]]) -> int:
    points = shapely.MultiPoint(list(path))
    pgon = points.buffer(0.5, cap_style='square')
    return length(pgon.exterior) + sum(length(p) for p in pgon.interiors)

totp1 = 0
totp2 = 0
for path in nx.components.connected_components(g):
    totp1 += len(path) * calcp1_perim(path)
    totp2 += len(path) * calcp2_perim(path)

print('P1 =', totp1)
print('P2 =', totp2)