2017: d16: ex1: add solution

2017/d16/ex1/ex1.py

@@ -0,0 +1,66 @@
+#!/usr/bin/env python
+
+import sys
+from typing import NamedTuple
+
+
+class Spin(NamedTuple):
+    n: int
+
+
+class Exchange(NamedTuple):
+    a: int
+    b: int
+
+
+class Partner(NamedTuple):
+    a: str
+    b: str
+
+
+Move = Spin | Exchange | Partner
+
+Programs = tuple[str, ...]
+
+
+def solve(input: str) -> str:
+    def parse_move(input: str) -> Move:
+        if input[0] == "s":
+            return Spin(int(input[1:]))
+        if input[0] == "x":
+            return Exchange(*map(int, input[1:].split("/")))
+        if input[0] == "p":
+            return Partner(*input[1:].split("/"))
+        assert False  # Sanity check
+
+    def parse(input: str) -> list[Move]:
+        return [parse_move(move) for move in input.strip().split(",")]
+
+    def apply_move(programs: Programs, move: Move) -> Programs:
+        match move:
+            case Spin(n):
+                return programs[-n:] + programs[:-n]
+            case Exchange(a, b):
+                tmp = list(programs)
+                tmp[a], tmp[b] = tmp[b], tmp[a]
+                return tuple(tmp)
+            case Partner(a, b):
+                ia, ib = programs.index(a), programs.index(b)
+                tmp = list(programs)
+                tmp[ia], tmp[ib] = tmp[ib], tmp[ia]
+                return tuple(tmp)
+
+    moves = parse(input)
+    programs = tuple(chr(ord("a") + i) for i in range(16))
+    for move in moves:
+        programs = apply_move(programs, move)
+    return "".join(programs)
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()