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minimax.py

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"""

Minimax helps to achieve maximum score in a game by checking all possible moves

depth is current depth in game tree.

nodeIndex is index of current node in scores[].

if move is of maximizer return true else false

leaves of game tree is stored in scores[]

height is maximum height of Game tree

"""

import math

from typing import List

def minimax(

depth: int, node_index: int, is_max: bool, scores: List[int], height: float

) -> int:

"""

>>> import math

>>> scores = [90, 23, 6, 33, 21, 65, 123, 34423]

>>> height = math.log(len(scores), 2)

>>> minimax(0, 0, True, scores, height)

65

>>> minimax(-1, 0, True, scores, height)

Traceback (most recent call last):

...

ValueError: Depth cannot be less than 0

>>> minimax(0, 0, True, [], 2)

Traceback (most recent call last):

...

ValueError: Scores cannot be empty

>>> scores = [3, 5, 2, 9, 12, 5, 23, 23]

>>> height = math.log(len(scores), 2)

>>> minimax(0, 0, True, scores, height)

12

"""

if depth < 0:

raise ValueError("Depth cannot be less than 0")

if len(scores) == 0:

raise ValueError("Scores cannot be empty")

if depth == height:

return scores[node_index]

if is_max:

return max(

minimax(depth + 1, node_index * 2, False, scores, height),

minimax(depth + 1, node_index * 2 + 1, False, scores, height),

)

return min(

minimax(depth + 1, node_index * 2, True, scores, height),

minimax(depth + 1, node_index * 2 + 1, True, scores, height),

)

def main() -> None:

scores = [90, 23, 6, 33, 21, 65, 123, 34423]

height = math.log(len(scores), 2)

print("Optimal value : ", end="")

print(minimax(0, 0, True, scores, height))

if __name__ == "__main__":

import doctest

doctest.testmod()

main()