Python/backtracking/minmax.py
Manish Kumar 5bfcab1aa4
Create minmax.py (#7409)
* Create minmax.py

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Co-authored-by: Christian Clauss <cclauss@me.com>
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2022-10-18 21:22:38 +02:00

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Python

"""
Minimax helps to achieve maximum score in a game by checking all possible moves.
"""
from __future__ import annotations
import math
def minimax(
depth: int, node_index: int, is_max: bool, scores: list[int], height: float
) -> int:
"""
depth is current depth in game tree.
node_index is index of current node in scores[].
scores[] contains the leaves of game tree.
height is maximum height of game tree.
>>> 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 not scores:
raise ValueError("Scores cannot be empty")
if depth == height:
return scores[node_index]
return (
max(
minimax(depth + 1, node_index * 2, False, scores, height),
minimax(depth + 1, node_index * 2 + 1, False, scores, height),
)
if is_max
else 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(f"Optimal value : {minimax(0, 0, True, scores, height)}")
if __name__ == "__main__":
import doctest
doctest.testmod()
main()