ass3: init halving_game

assignment3/halving_game.py

@@ -0,0 +1,76 @@
+import math
+
+State = tuple[int, int]  # Tuple of player (whose turn it is),
+# and the number to be decreased
+Action = str  # Decrement (number <- number-1) or halve (number <- number / 2)
+
+
+class Game:
+    def __init__(self, N: int):
+        self.N = N
+
+    def initial_state(self) -> State:
+        return 0, self.N
+
+    def to_move(self, state: State) -> int:
+        player, _ = state
+        return player
+
+    def actions(self, state: State) -> list[Action]:
+        return ["--", "/2"]
+
+    def result(self, state: State, action: Action) -> State:
+        _, number = state
+        if action == "--":
+            return (self.to_move(state) + 1) % 2, number - 1
+        else:
+            return (self.to_move(state) + 1) % 2, number // 2  # Floored division
+
+    def is_terminal(self, state: State) -> bool:
+        _, number = state
+        return number == 0
+
+    def utility(self, state: State, player: int) -> float:
+        assert self.is_terminal(state)
+        return 1 if self.to_move(state) == player else -1
+
+    def print(self, state: State):
+        _, number = state
+        print(f"The number is {number} and ", end="")
+        if self.is_terminal(state):
+            if self.utility(state, 0) > 0:
+                print(f"P1 won")
+            else:
+                print(f"P2 won")
+        else:
+            print(f"it is P{self.to_move(state)+1}'s turn")
+
+
+def minimax_search(game: Game, state: State) -> Action | None:
+    # YOUR CODE HERE
+    assert False, "Not implemented"
+
+
+game = Game(5)
+
+state = game.initial_state()
+game.print(state)
+while not game.is_terminal(state):
+    player = game.to_move(state)
+    action = minimax_search(game, state)  # The player whose turn it is
+    # is the MAX player
+    print(f"P{player+1}'s action: {action}")
+    assert action is not None
+    state = game.result(state, action)
+    game.print(state)
+
+# Expected output:
+# The number is 5 and it is P1's turn
+# P1's action: --
+# The number is 4 and it is P2's turn
+# P2's action: --
+# The number is 3 and it is P1's turn
+# P1's action: /2
+# The number is 1 and it is P2's turn
+# P2's action: --
+# The number is 0 and P1 won