2024: d11: ex2: add solution

2024/d11/ex2/ex2.py

@@ -0,0 +1,37 @@
+#!/usr/bin/env python
+
+import sys
+from collections import Counter
+
+
+def solve(input: str) -> int:
+    def parse(input: str) -> Counter[int]:
+        return Counter(int(n) for n in input.split())
+
+    def blink(stones: Counter[int]) -> Counter[int]:
+        res: Counter[int] = Counter()
+        for n, count in stones.items():
+            if n == 0:
+                res[1] += count
+            elif len(str(n)) % 2 == 0:
+                s = str(n)
+                lhs, rhs = s[: len(s) // 2], s[len(s) // 2 :]
+                res[int(lhs)] += count
+                res[int(rhs)] += count
+            else:
+                res[n * 2024] += count
+        return res
+
+    stones = parse(input)
+    for _ in range(75):
+        stones = blink(stones)
+    return sum(stones.values())
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()