Day 14 in Python

Author: mlukaszek

day14.py

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+import sys
+from collections import Counter
+
+def grow(template, formula, steps=10):
+    characterCounter = Counter(template)
+    
+    pairs = [ a+b for a,b in zip(template, template[1:])]
+    pairCounter = Counter(pairs)
+
+    for step in range(steps):
+        stepCounter = Counter()
+        for pair, count in pairCounter.items():
+            # Count the character being inserted
+            middleChar = formula[pair]
+            characterCounter[middleChar] += count
+
+            # Determine newly created pairs and count them, too
+            leftPair = pair[0] + middleChar
+            rightPair = middleChar + pair[1]
+            stepCounter[leftPair] += count
+            stepCounter[rightPair] += count
+
+        pairCounter = stepCounter
+    return characterCounter
+
+def main(args = ()):
+    fileName = "day14.txt" if len(args) < 1 else args[0]
+
+    formula = {}
+    template = ""
+    with open(fileName) as lines:
+        for line in lines:
+            line = line.strip()
+            if line and "->" not in line:
+                template = line
+            elif "->" in line:
+                pair, insert = line.split(" -> ")
+                formula[pair] = insert
+
+    for part, steps in enumerate((10, 40)):
+        counter = grow(template, formula, steps)
+        mc = counter.most_common()
+        print(f"Part {part+1}:", mc[0][1] - mc[-1][1])
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv[1:]))

day14.txt

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

day14sample.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