#!/usr/bin/env python
# 2021 - Advent Of Code - 14

from collections import Counter


def parse_file(file):
    with open(file) as f:
        poly_string = list(f.readline().strip())
        f.readline()
        insertion_rules = dict([line.strip().split(' -> ') for line in f.readlines()])

        return poly_string, insertion_rules


def step_poly(poly_str, ruleset):
    new_p = []
    for i, p in enumerate(poly_str):
        if i + 1 == len(poly_str):
            break
        new_p.append(p)
        binome = '' + p + poly_str[i+1]
        # print(f'binome {binome}')
        found = ruleset.get(binome)
        if found:
            # print(f'found: {found}')
            new_p.append(found)

    new_p.append(p)
    return ''.join(new_p)


# poly, rules = parse_file('input_example.txt')
poly, rules = parse_file('input.txt')
print(f'poly: {poly}')
print(f'rules: {rules}')

for s in range(13):
    print(f'step: {s}')
    poly = step_poly(poly, rules)
    #print(poly)

print(Counter(poly))
c = Counter(poly).most_common()[0][1] - Counter(poly).most_common()[-1][1]
print(c)