day 14

14/a.py

@@ -0,0 +1,41 @@
+from collections import defaultdict
+
+
+rules = {}
+
+
+# with open("sample.txt") as f:
+with open("input.txt") as f:
+    start_poly = f.readline().strip()
+    f.readline()
+    for line in f.readlines():
+        l, r = line.strip().split(" -> ")
+        rules[l] = r
+
+
+def mutate(poly):
+    new_poly = []
+    for i in range(0, len(poly)):
+        a = poly[i]
+        if i == len(poly) - 1:
+            new_poly.append(a)
+            break
+        b = poly[i + 1]
+        pair = a + b
+        new_poly.append(a)
+        new_poly.append(rules[pair])
+
+    return ''.join(new_poly)
+
+
+for i in range(0, 10):
+    start_poly = mutate(start_poly)
+
+counts = defaultdict(lambda: 0)
+
+for c in start_poly:
+    counts[c] += 1
+
+counts = sorted(counts.values())
+
+print(counts[-1] - counts[0])

14/b.py

@@ -0,0 +1,48 @@
+from collections import defaultdict
+
+
+rules = {}
+
+
+# with open("sample.txt") as f:
+with open("input.txt") as f:
+    sp = list(f.readline().strip())
+    f.readline()
+    for line in f.readlines():
+        l, r = line.strip().split(" -> ")
+        rules[l] = r
+
+
+start_poly = defaultdict(lambda: 0)
+for i in range(0, len(sp) - 1):
+    start_poly[sp[i] + sp[i + 1]] += 1
+
+
+def mutate(poly):
+    new_poly = defaultdict(lambda: 0)
+    for pair, count in poly.items():
+        new_c = rules[pair]
+        np1 = pair[0] + new_c
+        np2 = new_c + pair[1]
+        new_poly[np1] += count
+        new_poly[np2] += count
+    return new_poly
+
+
+def get_counts(d):
+    counts = defaultdict(lambda: 0)
+    for chars, count in d.items():
+        counts[chars[0]] += count  # only count 1st letter, the second was duplicated in a later pair
+
+    # except the last char in the original sequence
+    counts[sp[-1]] += 1
+
+    return dict(counts)
+
+
+for i in range(0, 40):
+    start_poly = mutate(start_poly)
+
+counts = sorted(get_counts(start_poly).values())
+
+print(counts[-1] - counts[0])

14/input.txt

@@ -0,0 +1,102 @@
+BNBBNCFHHKOSCHBKKSHN
+
+CH -> S
+KK -> V
+FS -> V
+CN -> P
+VC -> N
+CB -> V
+VK -> H
+CF -> N
+PO -> O
+KC -> S
+HC -> P
+PP -> B
+KO -> B
+BK -> P
+BH -> N
+CC -> N
+PC -> O
+FK -> N
+KF -> F
+FH -> S
+SS -> V
+ON -> K
+OV -> K
+NK -> H
+BO -> C
+VP -> O
+CS -> V
+KS -> K
+SK -> B
+OP -> S
+PK -> S
+HF -> P
+SV -> P
+SB -> C
+BC -> C
+FP -> H
+FC -> P
+PB -> N
+NV -> F
+VO -> F
+VH -> P
+BB -> N
+SF -> F
+NB -> K
+KB -> S
+VV -> S
+NP -> N
+SO -> O
+PN -> B
+BP -> H
+BV -> V
+OB -> C
+HV -> N
+PF -> B
+SP -> N
+HN -> N
+CV -> H
+BN -> V
+PS -> V
+CO -> S
+BS -> N
+VB -> H
+PV -> P
+NN -> P
+HS -> C
+OS -> P
+FB -> S
+HO -> C
+KH -> H
+HB -> K
+VF -> S
+CK -> K
+FF -> H
+FN -> P
+OK -> F
+SC -> B
+HH -> N
+OH -> O
+VS -> N
+FO -> N
+OC -> H
+NF -> F
+PH -> S
+HK -> K
+NH -> H
+FV -> S
+OF -> V
+NC -> O
+HP -> O
+KP -> B
+BF -> N
+NO -> S
+CP -> C
+NS -> N
+VN -> K
+KV -> N
+OO -> V
+SN -> O
+KN -> C
+SH -> F

14/sample.txt

@@ -0,0 +1,18 @@
+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