Intermediate Exercism • java

Queen Attack

Challenge Overview

Given the position of two queens on a chess board, indicate whether or not they are positioned so that they can attack each other.

Visit the queen-attack exercise on Exercism to read the full instructions and download the exercise files.

Dig Deeper

Difference Comparison Approach

class QueenAttackCalculator {
    private final Queen queen1;
    private final Queen queen2;
    
    QueenAttackCalculator(Queen queen1, Queen queen2) {
        if (queen1 == null || queen2 == null) {
            throw new IllegalArgumentException("You must supply valid positions for both Queens.");
        }
        if (queen1.getRow() == queen2.getRow() && queen1.getColumn() == queen2.getColumn()) {
            throw new IllegalArgumentException("Queens cannot occupy the same position.");
        }
        this.queen1 = queen1;
        this.queen2 = queen2;
    }

    boolean canQueensAttackOneAnother() {
        int rowDifference = Math.abs(queen1.getRow() - queen2.getRow());
        int columnDifference = Math.abs(queen1.getColumn() - queen2.getColumn());
        return rowDifference == 0 || columnDifference == 0 || rowDifference == columnDifference;
    }
}

Explanation

Constructor

The constructor takes two Queen objects, queen1 and queen2, and stores them as instance variables after validating the following conditions:

Either queen is null.
Both queens occupy the same position.

If either of these conditions is true, an exception is thrown.

`canQueensAttackOneAnother` Method

This method calculates the row and column differences between the two queens and checks the following conditions:

The row difference is zero (the queens are on the same row).
The column difference is zero (the queens are on the same column).
The row and column differences are equal (the queens are on the same diagonal).

If any of these conditions are true, the method returns true, indicating that the queens can attack each other.

Source: Exercism java/queen-attack