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day19a.py
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day19a.py
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from __future__ import print_function
import re
def find_all_replacements(base_molecule, match, replace):
indices = [m.start() for m in re.finditer(match, base_molecule)]
lm = len(match)
return [base_molecule[:i]+replace+base_molecule[i+lm:] for i in indices]
molecules = set()
test_molecule = 'HOHOHO'
molecules.update(find_all_replacements(test_molecule, 'H', 'HO'))
molecules.update(find_all_replacements(test_molecule, 'H', 'OH'))
molecules.update(find_all_replacements(test_molecule, 'O', 'HH'))
print(len(molecules))
# Part A
lines = [line for line in open('inputs/input19.txt')]
base_molecule = lines[-1].strip()
molecules = set()
for line in lines:
if '=>' not in line:
continue
match, _, replace = line.split()
molecules.update(find_all_replacements(base_molecule, match, replace))
print(len(set(molecules)))