2020/22

y2020/p22.py

+import sys
+
+
+def game(stack1, stack2, rec=False, N=1):
+    seen = set()
+    key = None
+    while stack1 and stack2:
+        key = (tuple(stack1), tuple(stack2))
+        a, b = stack1.pop(), stack2.pop()
+        if rec and key in seen:
+            return 0
+        elif rec and a <= len(stack1) and b <= len(stack2):
+            p2won = game(stack1[-a:], stack2[-b:], rec=rec, N=N + 1)
+        else:
+            p2won = b > a
+        seen.add(key)
+        winner = stack2 if p2won else stack1
+        order = [a, b] if p2won else [b, a]
+        winner[:] = order + winner
+    return sum(i * n for i, n in enumerate(winner, 1)) if N == 1 else p2won
+
+
+text = sys.stdin.read()
+p1, p2 = text.split('\n\n')
+stack1 = [int(n) for n in p1.splitlines()[1:]][::-1]
+stack2 = [int(n) for n in p2.splitlines()[1:]][::-1]
+print(game(stack1[:], stack2[:]))
+print(game(stack1[:], stack2[:], rec=True))