Given the position of two queens on a chess board, indicate whether or not they are positioned so that they can attack each other.
In the game of chess, a queen can attack pieces which are on the same row, column, or diagonal.
A chessboard can be represented by an 8 by 8 array.
So if you're told the white queen is at (2, 3) and the black queen at (5, 6), then you'd know you've got a set-up like so:
_ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _
_ _ _ W _ _ _ _
_ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _
_ _ _ _ _ _ B _
_ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _
You'd also be able to answer whether the queens can attack each other. In this case, that answer would be yes, they can, because both pieces share a diagonal.
Go to the root of your PHP exercise directory, which is <EXERCISM_WORKSPACE>/php
.
To find the Exercism workspace run
% exercism debug | grep Workspace
Get PHPUnit if you don't have it already.
% wget --no-check-certificate https://phar.phpunit.de/phpunit.phar
% chmod +x phpunit.phar
Execute the tests:
% ./phpunit.phar queen-attack/queen-attack_test.php
J Dalbey's Programming Practice problems http://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
<?php
require "queen-attack.php";
class QueenAttackTest extends PHPUnit\Framework\TestCase
{
/**
* Test a queen is placed in a valid position.
*/
public function testCreateQueenWithValidPosition()
{
$this->assertTrue(placeQueen(2, 2));
}
/**
* Test the queen is placed on a positive rank.
*
* @expectedException InvalidArgumentException
* @expectedExceptionMessage The rank and file numbers must be positive.
*/
public function testQueenHasPositiveRank()
{
placeQueen(-2, 2);
}
/**
* Test the queen has a rank on the board.
*
* @expectedException InvalidArgumentException
* @expectedExceptionMessage The position must be on a standard size chess board.
*/
public function testQueenHasRankOnBoard()
{
placeQueen(8, 4);
}
/**
* Test the queen is placed on a positive file.
*
* @expectedException InvalidArgumentException
* @expectedExceptionMessage The rank and file numbers must be positive.
*/
public function testQueenHasPositiveFile()
{
placeQueen(2, -2);
}
/**
* Test the queen has a file on the board.
*
* @expectedException InvalidArgumentException
* @expectedExceptionMessage The position must be on a standard size chess board.
*/
public function testQueenHasFileOnBoard()
{
placeQueen(4, 8);
}
/**
* Test if queens can attack each other.
*/
public function testQueensCanAttack()
{
$this->assertFalse(canAttack([2, 4], [6, 6]));
}
/**
* Test if queens can attack each other on the same rank.
*/
public function testQueensCanAttackOnSameRank()
{
$this->assertTrue(canAttack([2, 4], [2, 6]));
}
/**
* Test if queens can attack each other on the same file.
*/
public function testQueensCanAttackOnSameFile()
{
$this->assertTrue(canAttack([4, 5], [2, 5]));
}
/**
* Test if queens can attack each other on the first diagonal.
*/
public function testQueensCanAttackOnFirstDiagonal()
{
$this->assertTrue(canAttack([2, 2], [0, 4]));
}
/**
* Test if queens can attack each other on the second diagonal.
*/
public function testQueensCanAttackOnSecondDiagonal()
{
$this->assertTrue(canAttack([2, 2], [3, 1]));
}
/**
* Test if queens can attack each other on the third diagonal.
*/
public function testQueensCanAttackOnThirdDiagonal()
{
$this->assertTrue(canAttack([2, 2], [1, 1]));
}
/**
* Test if queens can attack each other on the fourth diagonal.
*/
public function testQueensCanAttackOnFourthDiagonal()
{
$this->assertTrue(canAttack([2, 2], [5, 5]));
}
}
<?php
// this is not a very good name for this function
// I would not expect it to return a bool
function placeQueen($rank, $file) {
if ($rank < 0 || $file < 0) {
throw new InvalidArgumentException("The rank and file numbers must be positive.");
}
if ($rank >= 8 || $file >= 8) {
throw new InvalidArgumentException("The position must be on a standard size chess board.");
}
return true;
}
function canAttack($whitePos, $blackPos) {
placeQueen($whitePos[0], $whitePos[1]);
placeQueen($blackPos[0], $blackPos[1]);
// horizontal or vertical attack
if ($whitePos[0] === $blackPos[0] || $whitePos[1] === $blackPos[1]) {
return true;
}
// diagonal attack
if (abs($whitePos[0] - $blackPos[0]) === abs($whitePos[1] - $blackPos[1])) {
return true;
}
return false;
}
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