advent_of_code_2021/day10/part2.py

import argparse
import functools

parser = argparse.ArgumentParser()
parser.add_argument("ifile", type=argparse.FileType('r'))
args = parser.parse_args()

ILLEGAL_CHARS = {
    ')': '(',
    ']': '[',
    '}': '{',
    '>': '<'
}


def protoBalance(stack, char):
    if stack is None:
        return None

    if char not in ILLEGAL_CHARS.keys():
        return stack + [char]
    else:
        prev = stack[-1]
        if prev != ILLEGAL_CHARS[char]:
            return None
        return stack[:-1]

filelines = args.ifile.readlines()
protoLines = filter(lambda line: functools.reduce(protoBalance, line, []) is not None, map(str.strip, filelines))

COMPLETION_CHARS = {
    '{': ('}', 3),
    '(': (')', 1),
    '[': (']', 2),
    '<': ('>', 4)
}

def protoComplete(seq: str):
    stack = functools.reduce(lambda stack, char: stack + [char] if char in COMPLETION_CHARS.keys() else stack[:-1], seq, [])
    return functools.reduce(lambda acc, val: acc * 5 + COMPLETION_CHARS[val][1], reversed(stack), 0)

scores = list(map(protoComplete, protoLines))
scores.sort()
print(scores[int(len(scores) / 2)])