StyleInCode

""" day_04_01.py """

# usage: python3 day_04_01.py < input

import sys


def access(item, layout):
    """ true if item has less than four neighbours """
    x, y = item
    return sum(1 for dy in [-1, 0, 1] for dx in [-1, 0, 1]
               if (x + dx, y + dy) in layout) < 5


with sys.stdin as infile:
    plan = {(i, j) for j, line in enumerate(infile)
            for i, symbol in enumerate(line.strip()) if symbol == '@'}

total = sum(1 for roll in plan if access(roll, plan))

print(total)

""" day_04_02.py """

# usage: python3 day_04_02.py < input

import sys


def access(item, layout):
    """ true if item has less than four neighbours """
    x, y = item
    return sum(1 for dy in [-1, 0, 1] for dx in [-1, 0, 1]
               if (x + dx, y + dy) in layout) < 5


def accessible(layout):
    """ true if at least one item is accessible """
    for item in layout:
        if access(item, layout):
            return True

    return False


with sys.stdin as infile:
    plan = {(i, j) for j, line in enumerate(infile)
            for i, symbol in enumerate(line.strip()) if symbol == '@'}

total = len(plan)

while accessible(plan):
    plan = {roll for roll in plan if not access(roll, plan)}

total = total - len(plan)

print(total)