day 14

Author: Mladjo Milunovic

day14/input

@@ -0,0 +1,102 @@
+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

day14/main.py

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+import os
+from pathlib import Path
+import itertools
+import functools
+from typing import List
+
+input_p = Path(os.getcwd()) / 'input'
+text = input_p.read_text()
+lines = text.splitlines()
+
+def line_to_rule(l):
+    split = l.split(" -> ")
+    return (split[0], split[1])
+
+start = lines[0]
+rules = [line_to_rule(l) for l in lines[2:]]
+rules_map = {r[0]: r[1] for r in rules}
+
+#part 1
+def do_step(polymer):
+    pairs = [polymer[i:i+2] for i in range(0, len(polymer) - 1)]
+    new_pairs = [p[0] + rules_map.get(p,"") + p[1] for p in pairs]
+
+    pairs_for_joining = [p if i == 0 else p[1:] for (i,p) in enumerate(new_pairs)]
+    new_polymer = "".join(pairs_for_joining)
+    return new_polymer
+
+polymer = start
+for i in range(10):
+    polymer = do_step(polymer)
+
+counts = {}
+for c in polymer:
+    counts[c] = counts.get(c, 0) + 1
+
+print(max(counts.values()) - min(counts.values()))
+print("####################")
+
+# part 2
+polymer = start
+
+pair_counts = {} # pair to count
+n_duplicates = {} #char to count
+
+#build initial pairs and initial duplicate characters (whenever a pair splits the new character is duplicated and propagated)
+pairs = [polymer[i:i+2] for i in range(0, len(polymer) - 1)]
+for p in pairs:
+    pair_counts[p] = pair_counts.get(p, 0) + 1
+    if p != pairs[0]:
+        n_duplicates[p[0]] = n_duplicates.get(p[0], 0) + 1
+
+
+for i in range(40):
+
+    pairs_to_add = {} #pair to count
+    pairs_to_remove = {} #pair to count
+
+    for (p, v) in pair_counts.items():
+        if p in rules_map:
+
+            new_char = rules_map[p]
+            n_duplicates[new_char] = n_duplicates.get(new_char, 0) +  v
+
+            n_p_1 = p[0] + new_char
+            n_p_2 = new_char + p[1]
+            
+            pairs_to_add[n_p_1] = pairs_to_add.get(n_p_1, 0) + v
+            pairs_to_add[n_p_2] = pairs_to_add.get(n_p_2, 0) + v
+
+            pairs_to_remove[p] = pairs_to_remove.get(p, 0) - v
+
+    for (p,v) in pairs_to_add.items():
+        pair_counts[p] = pair_counts.get(p, 0) + v
+    for (p,v) in pairs_to_remove.items():
+        pair_counts[p] += v
+
+
+chars = set()
+for (k,v) in pair_counts.items():
+    if v != 0:
+        chars.add(k[0])
+        chars.add(k[1])
+
+counts = {}
+for c in chars:
+    pairs_containing_char = [(k,v) for (k,v) in pair_counts.items() if k[0] == c or k[1] == c]
+    total = 0
+    for (k,v) in pairs_containing_char:
+
+        if k == c + c: #BB,CC...
+            total += 2 * v
+        else:
+            total += v
+    counts[c] = total - n_duplicates.get(c,0)
+    # print(c, ": ", total - n_duplicates.get(c, 0))
+
+print(max(counts.values()) - min(counts.values()))