[py] Solve 2021_14

py/2021/14.py

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+import argparse
+from pathlib import Path
+from collections import Counter
+
+def step(pairs, rules):
+    result = Counter()
+    for pair, amount in pairs.items():
+        if pair in rules:
+            a, b = rules[pair]
+            result[a] += amount
+            result[b] += amount
+        else:
+            result[pair] += amount
+    return result
+
+def count_chars(template, pairs):
+    chars = Counter()
+    for pair, amount in pairs.items():
+        chars[pair[0]] += amount
+    chars[template[-1]] += 1
+    return chars
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("file", type=Path)
+    args = parser.parse_args()
+
+    with open(args.file) as f:
+        template = next(f).strip()
+        next(f)
+        rules = {}
+        for line in f:
+            pair, char = line.strip().split(" -> ")
+            rules[pair] = (pair[0] + char, char + pair[1])
+
+    pairs = Counter(template[i:i+2] for i in range(len(template) - 1))
+
+    for i in range(10):
+        pairs = step(pairs, rules)
+
+    chars = count_chars(template, pairs).most_common()
+    print(f"Part 1: {chars[0][1] - chars[-1][1]}")
+
+    for i in range(30): # 40 steps total
+        pairs = step(pairs, rules)
+
+    chars = count_chars(template, pairs).most_common()
+    print(f"Part 2: {chars[0][1] - chars[-1][1]}")
+
+if __name__ == "__main__":
+    main()

py/2021/input_14.txt

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+BNSOSBBKPCSCPKPOPNNK
+
+HH -> N
+CO -> F
+BC -> O
+HN -> V
+SV -> S
+FS -> F
+CV -> F
+KN -> F
+OP -> H
+VN -> P
+PF -> P
+HP -> H
+FK -> K
+BS -> F
+FP -> H
+FN -> V
+VV -> O
+PS -> S
+SK -> N
+FF -> K
+PK -> V
+OF -> N
+VP -> K
+KB -> H
+OV -> B
+CH -> F
+SF -> F
+NH -> O
+NC -> N
+SP -> N
+NN -> F
+OK -> S
+BB -> S
+NK -> S
+FH -> P
+FC -> S
+OB -> P
+VS -> P
+BF -> S
+HC -> V
+CK -> O
+NP -> K
+KV -> S
+OS -> V
+CF -> V
+FB -> C
+HO -> S
+BV -> V
+KS -> C
+HB -> S
+SO -> N
+PH -> C
+PN -> F
+OC -> F
+KO -> F
+VF -> V
+CS -> O
+VK -> O
+FV -> N
+OO -> K
+NS -> S
+KK -> C
+FO -> S
+PV -> S
+CN -> O
+VC -> P
+SS -> C
+PO -> P
+BN -> N
+PB -> N
+PC -> H
+SH -> K
+BH -> F
+HK -> O
+VB -> P
+NV -> O
+NB -> C
+CP -> H
+NO -> K
+PP -> N
+CC -> S
+CB -> K
+VH -> H
+SC -> C
+KC -> N
+SB -> B
+BP -> P
+KP -> K
+SN -> H
+KF -> K
+KH -> B
+HV -> V
+HS -> K
+NF -> B
+ON -> H
+BO -> P
+VO -> K
+OH -> C
+HF -> O
+BK -> H

py/2021/input_14_example.txt

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+NNCB
+
+CH -> B
+HH -> N
+CB -> H
+NH -> C
+HB -> C
+HC -> B
+HN -> C
+NN -> C
+BH -> H
+NC -> B
+NB -> B
+BN -> B
+BB -> N
+BC -> B
+CC -> N
+CN -> C