Advent of Code Day 11 (Part 2)

AoC2020_day11_p2.py

import copy

def num_adj_occupied_2(x, y, in_array):
    num = 0
    dim_x, dim_y = len(in_array[0]), len(in_array)

    for ym in (-1, 0, 1):
        for xm in (-1, 0, 1):
            if ym == 0 and xm == 0: continue
            xp, yp = x+xm, y+ym
            while (xp >= 0 and xp < dim_x) and (yp >= 0 and yp < dim_y):
                view = in_array[yp][xp]
                if view != '.':
                    if view == '#':
                        num += 1
                    break
                xp += xm
                yp += ym
    return num

def do_round(in_array):
    out_array = copy.deepcopy(in_array)
    for y, row in enumerate(in_array):
        for x, seat in enumerate(row):
            if seat == 'L':
                if num_adj_occupied_2(x, y, in_array) == 0:
                    out_array[y][x] = '#'
            if seat == '#':
                if num_adj_occupied_2(x, y, in_array) >= 5:
                    out_array[y][x] = 'L'
    return out_array

array = [list(row.strip()) for row in open("input_11").readlines()]
prev_occ, num_occ = 0, 0

while True:
    array = do_round(array)
    prev_occ, num_occ = num_occ, sum([row.count('#') for row in array])
    if num_occ == prev_occ:
        print(num_occ)
        break