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#!/usr/bin/env python3
import aoc20
import sys
def read(lines):
board = {}
h = len(lines)
w = len(lines[0])
for y in range(h):
for x in range(w):
if lines[y][x] == "L":
board[(x, y)] = 0
elif lines[y][x] == ".":
board[(x, y)] = -1
return board, w, h
def amount_neighbours_occ(p, board):
amount = 0
for dy in range(-1, 1+1):
for dx in range(-1, 1+1):
if dy == dx == 0:
continue
new_p = (p[0] + dx, p[1] + dy)
if new_p in board and board[new_p] == 1:
amount += 1
return amount
def pt1(_in):
board, w, h = read(_in)
while True:
prev_board = board.copy()
for p, state in prev_board.items():
if state == 0:
# empty
if amount_neighbours_occ(p, prev_board) == 0:
board[p] = 1
if state == 1:
# occ
if amount_neighbours_occ(p, prev_board) >= 4:
board[p] = 0
if prev_board == board:
break
prev_board = board
res = 0
for _, state in board.items():
if state == 1:
res += 1
return res
def amount_in_sight_occ(p, board, w, h):
amount = 0
dirs = ((1, 0), (1, 1), (0, 1), (-1, 1), (-1, 0), (-1, -1), (0, -1), (1, -1))
for dir in dirs:
step = 0
while True:
step += 1
new_p = p[0] + dir[0] * step, p[1] + dir[1] * step
if new_p not in board:
break
if board[new_p] == -1:
continue
if board[new_p] == 1:
amount += 1
break
return amount
def pt2(_in):
board, w, h = read(_in)
while True:
prev_board = board.copy()
for p, state in prev_board.items():
if state == 0:
# empty
if amount_in_sight_occ(p, prev_board, w, h) == 0:
board[p] = 1
if state == 1:
# occ
if amount_in_sight_occ(p, prev_board, w, h) >= 5:
board[p] = 0
if prev_board == board:
break
prev_board = board
res = 0
for _, state in board.items():
if state == 1:
res += 1
return res
if __name__ == "__main__":
input = aoc20.read_input(sys.argv[1:], 11)
print(pt1(input))
print(pt2(input))
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