def test_parse_2():
replacements, molecule = parse_input(test_input_2)
assert len(replacements) == 3
assert replacements[0] == ('H', 'HO')
assert replacements[1] == ('H', 'OH')
assert replacements[2] == ('O', 'HH')
assert molecule == 'HOHOHO'
def test_replacements_1():
replacements, molecule = parse_input(test_input_1)
generated_molecules = do_replacements(molecule, replacements)
assert len(generated_molecules) == 4
assert 'HOOH' in generated_molecules
assert 'HOHO' in generated_molecules
assert 'OHOH' in generated_molecules
assert 'HHHH' in generated_molecules
def test_build_2_greedy():
replacements, _ = parse_input(build_replacements)
n_steps = build_molecule(replacements, 'HOHOHO', reverse=True, greedy=True)
assert n_steps == 6
def test_build_1_reverse():
replacements, _ = parse_input(build_replacements)
n_steps = build_molecule(replacements, 'HOH', reverse=True)
assert n_steps == 3
def test_build_2():
replacements, _ = parse_input(build_replacements)
n_steps = build_molecule(replacements, 'HOHOHO')
assert n_steps == 6
def test_part_1():
with open('input.txt') as f:
specs = f.read()
replacements, molecule = parse_input(specs)
generated_molecules = do_replacements(molecule, replacements)
assert len(generated_molecules) == 535
def test_replacements_2():
replacements, molecule = parse_input(test_input_2)
generated_molecules = do_replacements(molecule, replacements)
assert len(generated_molecules) == 7
def test_part_2():
with open('input.txt') as f:
specs = f.read()
replacements, molecule = parse_input(specs)
n_steps = build_molecule(replacements, target=molecule, reverse=True, greedy=True)
assert n_steps == 212
