day 14

1 files changed, 32 insertions, 0 deletions

diff --git a/14.py b/14.py
new file mode 100644
index 0000000..e2a8e05
--- /dev/null
+++ b/14.py
@@ -0,0 +1,32 @@
+from collections import Counter
+from itertools import pairwise
+from utils import open_day
+
+PairCounts = Counter[tuple[str, str]]
+
+with open_day(14) as f:
+    chunks = f.read().rstrip().split('\n\n')
+    template = chunks[0]
+    rules = { (p[0][0], p[0][1]): p[1] for p in (l.split(' -> ') for l in chunks[1].split('\n')) }
+
+def step(pairs: PairCounts, rules: list[str, str]) -> PairCounts:
+    newcount: PairCounts = Counter()
+    for pair, count in pairs.items():
+        insert = rules[pair]
+        newcount[(pair[0], insert)] += count
+        newcount[(insert, pair[1])] += count
+    return newcount
+
+def solution(pairs: PairCounts, template: str) -> int:
+    c = Counter()
+    for pair, count in pairs.items():
+        c[pair[0]] += count
+    c[template[-1]] += 1
+    common = c.most_common()
+    return common[0][1] - common[-1][1]
+
+pairs = Counter(pairwise(template))
+for _ in range(10): pairs = step(pairs, rules)
+print(solution(pairs, template))
+for _ in range(30): pairs = step(pairs, rules)
+print(solution(pairs, template))