2022: d13: ex1: add solution

2022/d13/ex1/ex1.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python
+
+import sys
+from typing import Union
+
+Packet = Union[int, list["Packet"]]
+
+
+def cmp_packet(lhs: Packet, rhs: Packet) -> int:
+    if isinstance(lhs, int) and isinstance(rhs, int):
+        return lhs - rhs
+    if isinstance(lhs, int):
+        lhs = [lhs]
+    if isinstance(rhs, int):
+        rhs = [rhs]
+    non_equal_cmp = (res for res in map(cmp_packet, lhs, rhs) if res != 0)
+    len_cmp = cmp_packet(len(lhs), len(rhs))
+    return next(non_equal_cmp, len_cmp)
+
+
+def solve(input: list[str]) -> int:
+    def to_packets(input: str) -> tuple[Packet, Packet]:
+        first, second = input.splitlines()
+        return eval(first), eval(second)  # Secret best way to parse JSON
+
+    return sum(
+        i
+        for i, packets in enumerate(input, start=1)
+        if cmp_packet(*to_packets(packets)) <= 0
+    )
+
+
+def main() -> None:
+    input = sys.stdin.read().split("\n\n")
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()