AoC02.py

AoC02.py

'''AoC 2018 #02, safari-https://adventofcode.com/2018/day/2 - Olaf, 2 Dec 2018'''

import collections, functools, operator, typing

with open('AoC02.txt') as file:
    ids = tuple(map(str.strip, file.readlines()))

def freq_counts(s: str) -> typing.Iterable[int]:
    '''frequency counts >1 that apply to chars in string s
    >>> ids = 'abcdef bababc abbcde abcccd aabcdd abcdee ababab'.split() # from AoC explanation
    >>> print(*map(freq_counts, ids))
    set() {2, 3} {2} {3} {2} {2} {3}'''
    return set(collections.Counter(s).values()) - {1}

freq_count_counts = collections.Counter()
for id in ids:
    freq_count_counts.update(freq_counts(id))

print('first answer', functools.reduce(operator.mul, freq_count_counts.values()))
    
def equal_but_1(a: str, b: str) -> bool:
    '''True iff a == b but for 1 position in a and b'''
    return sum(map(operator.ne, a, b)) == 1
    
def equal_but_1_pairs(ids: typing.Iterable[str]) -> typing.Iterator[typing.Tuple[str, str]]:
    '''pairs (a, b) in ids x ids for which a == b but for 1 position in a and b
    if (a, b) occur in results, (b, a) doesn't by only testing a triangle from the ids x ids square
    >>> ids = 'abcde fghij klmno pqrst fguij axcye wvxyz'.split()
    >>> print(*equal_but_1_pairs(ids))
    ('fghij', 'fguij')'''
    for i, a in enumerate(ids):
        for b in ids[i+1:]:
            if equal_but_1(a, b):
                yield a, b

pairs = tuple(equal_but_1_pairs(ids))
assert len(pairs) == 1, 'AoC suggests unique solution'
pair = pairs[0]
print('second answer', ''.join(a for a, b in zip(*pair) if a == b))

# --- main
if __name__ == '__main__':
    import doctest
    doctest.testmod()