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aoc_2021_14_test.py
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aoc_2021_14_test.py
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# https://adventofcode.com/2021/day/14
# Time taken
# 1st part: 1h 0m
# 2nd part: 0h 2m
# NNCB
# 3 pairs, length = 4
# NCNBCHB
# NN -> C => NC and CN
# NC -> B => NB and BC
# CB -> H => CH and HC
# 6 pairs, length = 7
# At each iteration, each pair leads to two new pairs.
from pathlib import Path
import unittest
import re
def parse_coords(line):
return list(map(int, line.split(",")))
def parse_rule(line):
pattern = "([A-Z]{2}) -> ([A-Z])"
match = re.search(pattern, line)
return (match.group(1), match.group(2))
def parse_lines(lines):
polymer = lines[0]
rules = [parse_rule(line) for line in lines[2:]]
return polymer, rules
def get_data(file):
with open(Path(__file__).parent / file) as f:
lines = f.read().splitlines()
return parse_lines(lines)
def get_pairs_map(polymer):
pairs = [polymer[i : i + 2] for i in range(len(polymer) - 1)]
pairs_map = {}
for pair in pairs:
if pair in pairs_map:
pairs_map[pair] += 1
else:
pairs_map[pair] = 1
return pairs_map
def get_rules_map(rules):
rules_map = {}
for rule in rules:
pair = rule[0]
new_element = rule[1]
new_pairs = [pair[0] + new_element, new_element + pair[1]]
rules_map[pair] = new_pairs
return rules_map
def do_pair_insertion(polymer_map, rules_map):
new_polymer_map = {}
for polymer in polymer_map:
new_pairs = rules_map[polymer]
for new_pair in new_pairs:
if new_pair in new_polymer_map:
new_polymer_map[new_pair] += polymer_map[polymer]
else:
new_polymer_map[new_pair] = polymer_map[polymer]
return new_polymer_map
def grow_polymer(polymer, rules, steps):
rules_map = get_rules_map(rules)
pairs_map = get_pairs_map(polymer)
for _ in range(steps):
pairs_map = do_pair_insertion(pairs_map, rules_map)
return pairs_map
def get_element_count(pairs_map, original_polymer):
element_map = {}
last_letter = original_polymer[-1]
for pair in pairs_map:
letter = pair[0]
if letter in element_map:
element_map[letter] += pairs_map[pair]
else:
element_map[letter] = pairs_map[pair]
if last_letter in element_map:
element_map[last_letter] += 1
else:
element_map[last_letter] = 1
return element_map
def find_least_and_most_common_count_difference(element_map):
most_common_count = max(element_map.values())
least_common_count = min(element_map.values())
return most_common_count - least_common_count
def predict_polymer_growth(polymer, rules, steps=10):
pairs_map = grow_polymer(polymer, rules, steps)
element_map = get_element_count(pairs_map, polymer)
return find_least_and_most_common_count_difference(element_map)
class MyTest(unittest.TestCase):
def test_solve_part_1(self):
polymer, rules = get_data("test_input.txt")
received = predict_polymer_growth(polymer, rules)
expected = 1588
self.assertEqual(received, expected)
if __name__ == "__main__":
# unittest.main()
polymer, rules = get_data("input.txt")
part1 = predict_polymer_growth(polymer, rules)
print(part1)
part2 = predict_polymer_growth(polymer, rules, 40)
print(part2)