5 Best Ways to Check if a Queen Can Attack a Given Cell on a Chessboard in Python

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πŸ’‘ Problem Formulation: In the game of chess, the queen is the most powerful piece, capable of attacking in any direction for any number of squares. But how can we determine if a queen can attack a specific cell? Given a chessboard represented as a two-dimensional grid, a queen’s position, and a target cell, we seek Python solutions to verify if the target can be attacked by the queen. For instance, inputting the positions (2, 3) for the queen and (5, 6) for the target cell, the expected output would be False, as a queen cannot attack diagonally at such angles.

Method 1: Using Basic Chess Rules

This method involves checking if the target cell is in the same row, column, or diagonal as the queen. In Python, we’d compare the row and column indices of the queen’s position with those of the target cell to determine attack capability.

Here’s an example:

def can_queen_attack(queen_position, target_position):
    return (queen_position[0] == target_position[0] or
            queen_position[1] == target_position[1] or
            abs(queen_position[0] - target_position[0]) == abs(queen_position[1] - target_position[1]))

queen_pos = (3, 5)
target_pos = (6, 8)
print(can_queen_attack(queen_pos, target_pos))

Output:

True

In this code, we check for three possible scenarios: if the queen and the target cell share the same row (queen_position[0] == target_position[0]), the same column (queen_position[1] == target_position[1]), or lie on the same diagonal (difference between rows is equal to the difference between columns). The function returns True if any of these conditions holds, signifying the queen can attack the target cell.

Method 2: Object-Oriented Approach

This object-oriented approach defines a class Queen that can determine if it can attack another cell. The advantage here is encapsulation and the potential to extend functionality to include more chess logic later on.

Here’s an example:

class Queen:
    def __init__(self, position):
        self.position = position

    def can_attack(self, target_position):
        return (self.position[0] == target_position[0] or
                self.position[1] == target_position[1] or
                abs(self.position[0] - target_position[0]) == abs(self.position[1] - target_position[1]))

queen = Queen((3, 5))
target_pos = (6, 8)
print(queen.can_attack(target_pos))

Output:

True

The Queen class is initialized with a position. The can_attack method is essentially the same as in Method 1, but it is now associated with an object that maintains state. This abstraction makes the functionality more versatile, allowing further additions to the class without changing the interface for attack checks.

Method 3: Matrix Representation

This method uses a matrix to represent the chessboard with binary values: 1 represents the queen’s reach, and 0 represents safe cells. This method visually maps attack paths, which can help in more complex scenarios.

Here’s an example:

def matrix_queen_attack(grid_size, queen_position, target_position):
    board = [[0 for _ in range(grid_size)] for _ in range(grid_size)]
    x, y = queen_position
    for i in range(grid_size):
        for j in range(grid_size):
            if i == x or j == y or abs(i - x) == abs(j - y):
                board[i][j] = 1
    return bool(board[target_position[0]][target_position[1]])

grid_size = 8
queen_pos = (3, 5)
target_pos = (6, 8)
print(matrix_queen_attack(grid_size, queen_pos, target_pos))

Output:

True

We create a board of zeros with dimensions equal to the chessboard size. Then, we iterate through the matrix, marking cells the queen can attack with 1. The target cell’s value indicates whether it’s under attack. This method provides a clear visual representation at the expense of more memory and potentially longer execution time for large boards.

Method 4: Functional Programming Style

In a functional programming style, we aim to solve the problem using pure functions and expressions. This style can lead to more concise and potentially more readable code.

Here’s an example:

can_queen_attack = lambda q, t: q[0] == t[0] or q[1] == t[1] or abs(q[0] - t[0]) == abs(q[1] - t[1])

queen_pos = (3, 5)
target_pos = (6, 8)
print(can_queen_attack(queen_pos, target_pos))

Output:

True

This lambda function is a condensed version of Method 1’s function. It checks the same three conditions (row, column, diagonal) to determine if the queen can attack. This functional approach is compact and eliminates the need for explicit function definitions. However, it can sacrifice readability for those unfamiliar with lambda expressions or when used in more complex functions.

Bonus One-Liner Method 5: Direct Comparison

A direct comparison one-liner combines all required checks in just one statement. It’s a quick and dirty method for those who value brevity above all else.

Here’s an example:

queen_pos = (3, 5)
target_pos = (6, 8)
print(queen_pos[0] == target_pos[0] or queen_pos[1] == target_pos[1] or abs(queen_pos[0] - target_pos[0]) == abs(queen_pos[1] - target_pos[1]))

Output:

True

The one-liner directly checks the positions for row, column, and diagonal attack capabilities. While this method is extremely concise, it isn’t reusable unless copied wherever needed, which isn’t recommended for maintainability. It’s not considered good practice in the real-world applications but could be useful in quick scripts or for algorithm challenges.

Summary/Discussion

  • Method 1: Basic Chess Rules. Straightforward and easy to understand. Limited to this specific problem.
  • Method 2: Object-Oriented Approach. Encapsulates functionality which is great for scalability and maintainability. More complex than necessary for simple problems.
  • Method 3: Matrix Representation. Visually maps the board, which can be useful for understanding more complex scenarios. Uses more memory and computation time.
  • Method 4: Functional Programming Style. It offers concise code and is elegant for those accustomed to functional paradigms. Can be less readable for those not familiar with such approaches.
  • Method 5: Direct Comparison One-Liner. The most concise solution but is not reusable and lacks modularity. Best for very specific, one-off cases.