72 lines
1.9 KiB
Python
72 lines
1.9 KiB
Python
import re
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input_pattern = re.compile(r"([A-Z]+) -> ([A-Z]+)")
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def load():
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with open("../.input/day14", "r") as f:
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start, rest = f.read().split("\n\n")
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return start, input_pattern.findall(rest)
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def step(start, rules):
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output = []
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for pair in zip(start, start[1:]):
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c1, c2 = pair
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output.append(c1)
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output.append(rules[c1 + c2])
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output.append(start[-1])
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return output
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def find_counts(start: str, rules: dict[str, str], epochs: int) -> dict[str, int]:
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for _ in range(epochs):
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start = step(start, rules)
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chars: dict[str, int] = {}
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for c in start:
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chars[c] = chars.get(c, 0) + 1
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return chars
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def solve1() -> int:
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start, rules = load()
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rules = {k: v for k, v in rules}
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chars = find_counts(start, rules, 10)
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values = list(sorted(chars.values(), reverse=True))
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return values[0] - values[-1]
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def find_counts_optimized(start: str, rules: dict[str, str], epochs: int) -> dict[str, int]:
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chars: dict[str, int] = {}
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for c1, c2 in zip(start, start[1:]):
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chars[c1 + c2] = chars.get(c1 + c2, 0) + 1
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for _ in range(epochs):
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new_chars: dict[str, int] = {}
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for combo, count in chars.items():
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if combo in rules:
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insert = rules[combo]
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new_chars[combo[0] + insert] = new_chars.get(combo[0] + insert, 0) + chars[combo]
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new_chars[insert + combo[1]] = new_chars.get(insert + combo[1], 0) + chars[combo]
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chars = new_chars
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final_chars: dict[str, int] = {start[-1]: 1}
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for combo, count in chars.items():
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final_chars[combo[0]] = final_chars.get(combo[0], 0) + count
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return final_chars
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def solve2():
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start, rules = load()
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rules = {k: v for k, v in rules}
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chars = find_counts_optimized(start, rules, 40)
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values = list(sorted(chars.values(), reverse=True))
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return values[0] - values[-1]
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if __name__ == "__main__":
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print(solve1())
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print(solve2())
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