day14

.gitignore

@@ -1,5 +1,7 @@
 *.in
 .metals/
+profile.txt
 
 # binaries
 day??
+target/

day14.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+import fileinput
+from timeit import timeit
+from collections import Counter, defaultdict
+
+lines = [str(line) for line in fileinput.input()]
+
+
+def main():
+    template = [ord(c) for c in lines[0].strip()]
+    rules = defaultdict(dict)
+    for l in lines[2:]:
+        rules[ord(l[0])][ord(l[1])] = ord(l[6])
+
+    polymer_counter = Counter(template)
+
+    counter = defaultdict(lambda: defaultdict(int))
+    for i in range(len(template) - 1):
+        counter[template[i]][template[i + 1]] += 1
+
+    def step():
+        nonlocal counter
+
+        new_counter = defaultdict(lambda: defaultdict(int))
+        for a, subcounter in counter.items():
+            for c, count in subcounter.items():
+                b = rules[a][c]
+                new_counter[a][b] += count
+                new_counter[b][c] += count
+                polymer_counter[b] += count
+        counter = new_counter
+
+    def run(iterations):
+        for _ in range(iterations):
+            step()
+
+        counts = polymer_counter.most_common()
+        return counts[0][1] - counts[-1][1]
+
+    part1 = run(10)
+    part2 = run(30)  # 30 because it inherits the state from part 1
+
+    return part1, part2
+
+
+if __name__ == "__main__":
+    print(main())
+    print(f"{timeit(main, number=2000) / 2:.3f} ms")