Challenge 18

Challenge 18.1



In [59]:

    
myinput = '/home/fmuinos/projects/adventofcode/2016/ferran/inputs/input18.txt'

safe tiles (.) and traps (^)



In [60]:

    
trap_dict = {True: '^', False: '.'}



In [61]:

    
def parse_input(myinput):
    with open(myinput, 'rt') as f:
        return next(f).rstrip()



In [62]:

    
parse_input(myinput)









    Out[62]:





'.^^^.^.^^^.^.......^^.^^^^.^^^^..^^^^^.^.^^^..^^.^.^^..^.^..^^...^.^^.^^^...^^.^.^^^..^^^^.....^....'



In [83]:

    
def trap(left, center, right):
    cond = []
    cond.append((left and center) and not right)
    cond.append((center and right) and not left)
    cond.append(left and ((not center) and (not right)))
    cond.append(right and ((not left) and (not center)))
    for item in cond:
        if item:
            return True
    return False

def next_row(row):
    new_row = []
    for i in range(len(row)):
        if i == 0:
            left = False
        else:
            left = (row[i-1] == '^')
        center = (row[i] == '^')
        if i == len(row) - 1:
            right = False
        else:
            right = (row[i+1] == '^')
        new_row.append(trap_dict[trap(left, center, right)])
    return ''.join(new_row)

def count_safe(row, n):
    safe = row.count('.')
    for i in range(n-1):
        row = next_row(row)
        safe += row.count('.')
    return safe

Tests



In [85]:

    
count_safe('..^^.', 3)









    Out[85]:





6



In [86]:

    
count_safe('.^^.^.^^^^', 10)









    Out[86]:





38

Result



In [87]:

    
row = parse_input(myinput)
count_safe(row, 40)









    Out[87]:





2013

Challenge 18.2



In [88]:

    
row = parse_input(myinput)
count_safe(row, 400000)









    Out[88]:





20006289