day22

day22.py

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+from collections import deque
+
+
+def read_decks():
+    with open('day22/input') as reader:
+        first, second = reader.read().split('\n\n')
+        player1 = [int(i) for i in first.split('\n')[1:]]
+        player2 = [int(i) for i in second.split('\n')[1:] if i != '']
+        return deque(player1), deque(player2)
+
+
+def play_part1(player1, player2):
+    while player1 and player2:
+        p1_top = player1.popleft()
+        p2_top = player2.popleft()
+
+        if p1_top > p2_top:
+            player1.append(p1_top)
+            player1.append(p2_top)
+        else:
+            player2.append(p2_top)
+            player2.append(p1_top)
+
+    return player1, player2
+
+
+def calc_result(deck):
+    return sum([(i+1) * card for i, card in enumerate(reversed(deck))])
+
+
+player1, player2 = read_decks()
+
+# beware part one does not work in case of recursion, as there is no recursion rule yet
+player1_part1, player2_part1 = play_part1(deque(player1), deque(player2))
+
+
+winner_deck_part1 = player1_part1 if player1_part1 else player2_part1
+
+res_part1 = calc_result(winner_deck_part1)
+
+print(res_part1)
+
+
+def play_part2(player1, player2):
+    states = set()
+    while player1 and player2:
+        p1_top = player1.popleft()
+        p2_top = player2.popleft()
+
+        new_state = (p1_top, p2_top, tuple(player1), tuple(player2))
+        if new_state in states:
+            return True, None, None  # player 1 won, but do not return decks in case of errors. Should not happen in case of normal input, except recursive test case ;)
+        states.add(new_state)
+
+        if len(player1) >= p1_top and len(player2) >= p2_top:
+            player1_subgame = deque(list(player1)[:p1_top])
+            player2_subgame = deque(list(player2)[:p2_top])
+            player1_won, _, _ = play_part2(player1_subgame, player2_subgame)
+            if player1_won:
+                player1.append(p1_top)
+                player1.append(p2_top)
+            else:
+                player2.append(p2_top)
+                player2.append(p1_top)
+        else:
+            if p1_top > p2_top:
+                player1.append(p1_top)
+                player1.append(p2_top)
+            else:
+                player2.append(p2_top)
+                player2.append(p1_top)
+
+    return bool(player1), player1, player2
+
+
+player1_won, player1_part2, player2_part2 = play_part2(player1, player2)
+
+winner_deck_part2 = player1_part2 if player1_won else player2_part2
+
+res_part2 = calc_result(winner_deck_part2)
+
+print(res_part2)