ACSL 2018 Compressed Lists Problem

ACSL2018CompressedLists.py

#!/usr/bin/env python
"""
http://www.acsl.org/17-18/allstar/2.%20Compressed%20Lists.pdf
"""
import fileinput
from collections import Counter


def compress_list(_list, frequency, out=None):
    if out is None:
        out = set([])

    frequency_check_list = [x[1] for x in _list if x[0] == frequency]
    for i in frequency_check_list:
        out.add(i)

    try:
        terms = [_list.pop(0), _list.pop(0)]
    except IndexError:
        out = sorted(''.join(out))
        out = ''.join(out)
        if not out:
            out = 'NONE'
        return out

    frequency_total = 0
    letters = ''
 
    for term in terms:
        _frequency, _letters = term
        frequency_total += _frequency
        letters += _letters

    compressed = (frequency_total, ''.join(sorted(letters)))
    _list.append(compressed)
    _list = sorted(_list, key=lambda x: (x[0], x[1]))

    return compress_list(_list, frequency, out)


def run(string, frequency):
    counter = Counter(string)
    frequency_list = list(zip(counter.values(), counter.keys()))
    sorted_list = sorted(frequency_list, key=lambda x: (x[0], x[1]))
    print(compress_list(sorted_list, frequency))


if __name__ == '__main__':
    for line in fileinput.input():
        string, frequency = line.split()
        if string.startswith('#'):
            continue
        print(string, frequency)
        run(string, int(frequency))