Day 14

day14/input.txt

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

day14/part1.py

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+#!/usr/bin/env python3
+import re
+from collections import Counter
+
+lines = (x.strip() for x in open("input.txt"))
+first = next(lines)
+
+combinations = Counter(first[a:a+2] for a in range(len(first)-1))
+replacements = dict()
+
+next(lines)
+
+for line in lines:
+    before, insert = re.match(r"([A-Z]{2}) -> ([A-Z])", line).groups()
+    replacements[before] = (before[0]+insert, insert+before[1])
+
+for _ in range(10):
+    nxt = {}
+    for before, afters in replacements.items():
+        for after in afters:
+            add = combinations.get(before, 0) + nxt.get(after, 0)
+            if add:
+                nxt[after] = add
+    combinations = nxt
+
+letters = {}
+for key, cnt in combinations.items():
+    letters[key[0]] = letters.get(key[0], 0) + cnt
+    letters[key[1]] = letters.get(key[1], 0) + cnt
+
+print(letters)
+print((max(*letters.values())+1) // 2 - (min(*letters.values())+1) // 2)

day14/part2.py

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+#!/usr/bin/env python3
+import re
+from collections import Counter
+
+lines = (x.strip() for x in open("input.txt"))
+first = next(lines)
+
+combinations = Counter(first[a:a+2] for a in range(len(first)-1))
+replacements = dict()
+
+next(lines)
+
+for line in lines:
+    before, insert = re.match(r"([A-Z]{2}) -> ([A-Z])", line).groups()
+    replacements[before] = (before[0]+insert, insert+before[1])
+print(combinations)
+
+for _ in range(40):
+    nxt = {}
+    for before, afters in replacements.items():
+        for after in afters:
+            add = combinations.get(before, 0) + nxt.get(after, 0)
+            if add:
+                nxt[after] = add
+    combinations = nxt
+    print(combinations)
+
+letters = {}
+for key, cnt in combinations.items():
+    letters[key[0]] = letters.get(key[0], 0) + cnt
+    letters[key[1]] = letters.get(key[1], 0) + cnt
+
+print(letters)
+print((max(*letters.values())+1) // 2 - (min(*letters.values())+1) // 2)