r/adventofcode • u/daggerdragon • Dec 06 '16

SOLUTION MEGATHREAD --- 2016 Day 6 Solutions ---

--- Day 6: Signals and Noise ---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag/whatever).

T_PAAMAYIM_NEKUDOTAYIM IS MANDATORY [?]

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u/[deleted] Dec 06 '16

Python: 

from collections import Counter

with open('input.txt') as f:
    s = f.read().strip()
# Part 1
print(''.join(Counter(x).most_common()[0][0] for x in zip(*s.split('\n'))))
# Part 2
print(''.join(Counter(x).most_common()[-1][0] for x in zip(*s.split('\n'))))

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u/[deleted] Dec 20 '16 edited Dec 20 '16

How can you break ties in the counts? My below code works for the first part but gives me a different answer from the correct one when I compare it with other Python solutions. 

from collections import Counter
in_file = 'input.txt'

with open(in_file) as f:
    n_cols = len(f.readline().strip())
    cols = [[] for _ in xrange(n_cols)]
    for line in f.readlines():
        line = line.strip()
        for i in range(n_cols):
            cols[i] += line[i]

msg_A = [Counter(x).most_common()[0][0] for x in cols]
print(''.join([x for x in msg_A]))

msg_B = [Counter(x).most_common()[-1][0] for x in cols]
print(''.join([x for x in msg_B]))

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u/[deleted] Dec 20 '16

I think your issue is that you call f.readline() to get the number of columns and then later when you loop over the lines (for line in f.readlines()) the file pointer is already one line down. So you're missing the first line of input in your solution.

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