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to Queen Attack in the Delphi Pascal Track

Published at Jul 31 2020 · 0 comments
Instructions
Test suite
Solution

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.

Testing

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For example, if you're submitting ubob.pas for the Bob exercise, the submit command would be something like exercism submit <path_to_exercism_dir>/delphi/bob/ubob.pas.

Source

J Dalbey's Programming Practice problems http://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html

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uQueenAttackTests.pas

unit uQueenAttackTests;

interface
uses
  DUnitX.TestFramework, uQueenAttack;

const
  CanonicalVersion = '2.3.0.1';

type
  [TestFixture('Creation of queens with valid and invalid positions')]
  TQueenCreationTests = class(TObject)
  public
    [Test]
//    [Ignore('Comment the "[Ignore]" statement to run the test')]
    procedure queen_with_a_valid_position;

    [Test]
    [Ignore]
    procedure queen_must_have_positive_row;

    [Test]
    [Ignore]
    procedure queen_must_have_row_on_board;

    [Test]
    [Ignore]
    procedure queen_must_have_positive_column;

    [Test]
    [Ignore]
    procedure queen_must_have_column_on_board;
  end;

  [TestFixture('Ability of one queen to attack another')]
  TQueenAttackTests = class(TObject)
  private
    WhiteQueen: TQueen;
    BlackQueen: TQueen;
  public
    [Test]
    [Ignore]
    procedure can_not_attack;

    [Test]
    [Ignore]
    procedure can_attack_on_same_row;

    [Test]
    [Ignore]
    procedure can_attack_on_same_column;

    [Test]
    [Ignore]
    procedure can_attack_on_first_diagonal;

    [Test]
    [Ignore]
    procedure can_attack_on_second_diagonal;

    [Test]
    [Ignore]
    procedure can_attack_on_third_diagonal;

    [Test]
    [Ignore]
    procedure can_attack_on_fourth_diagonal;
  end;

implementation
uses
  System.SysUtils;

{$REGION 'TQueenCreationTests'}

procedure TQueenCreationTests.queen_must_have_column_on_board;
begin
  Assert.WillRaise(procedure
    begin
      TQueen.Create(4, 8)
    end, EArgumentException, 'column not on board');

end;

procedure TQueenCreationTests.queen_must_have_positive_column;
begin
  Assert.WillRaise(procedure
    begin
      TQueen.Create(2, -2)
    end, EArgumentException, 'column not positive');
end;

procedure TQueenCreationTests.queen_must_have_positive_row;
begin
  Assert.WillRaise(procedure
    begin
      TQueen.Create(-2, 2)
    end, EArgumentException, 'row not positive');
end;

procedure TQueenCreationTests.queen_must_have_row_on_board;
begin
  Assert.WillRaise(procedure
    begin
      TQueen.Create(8, 4)
    end, EArgumentException, 'row not on board');
end;

procedure TQueenCreationTests.queen_with_a_valid_position;
begin
  Assert.WillNotRaise(
    procedure
    begin
      TQueen.Create(2, 2)
    end, EArgumentException);
end;

{$ENDREGION}

{$REGION 'TQueenAttackTests'}

procedure TQueenAttackTests.can_attack_on_first_diagonal;
begin
  WhiteQueen := TQueen.Create(2, 2);
  BlackQueen := TQueen.Create(0, 4);
  Assert.IsTrue(WhiteQueen.CanAttack(BlackQueen));
end;

procedure TQueenAttackTests.can_attack_on_fourth_diagonal;
begin
  WhiteQueen := TQueen.Create(1, 7);
  BlackQueen := TQueen.Create(0, 6);
  Assert.IsTrue(WhiteQueen.CanAttack(BlackQueen));
end;

procedure TQueenAttackTests.can_attack_on_same_column;
begin
  WhiteQueen := TQueen.Create(4, 5);
  BlackQueen := TQueen.Create(2, 5);
  Assert.IsTrue(WhiteQueen.CanAttack(BlackQueen));
end;

procedure TQueenAttackTests.can_attack_on_same_row;
begin
  WhiteQueen := TQueen.Create(2, 4);
  BlackQueen := TQueen.Create(2, 6);
  Assert.IsTrue(WhiteQueen.CanAttack(BlackQueen));
end;

procedure TQueenAttackTests.can_attack_on_second_diagonal;
begin
  WhiteQueen := TQueen.Create(2, 2);
  BlackQueen := TQueen.Create(3, 1);
  Assert.IsTrue(WhiteQueen.CanAttack(BlackQueen));
end;

procedure TQueenAttackTests.can_attack_on_third_diagonal;
begin
  WhiteQueen := TQueen.Create(2, 2);
  BlackQueen := TQueen.Create(1, 1);
  Assert.IsTrue(WhiteQueen.CanAttack(BlackQueen));
end;

procedure TQueenAttackTests.can_not_attack;
begin
  WhiteQueen := TQueen.Create(2, 4);
  BlackQueen := TQueen.Create(6, 6);
  Assert.IsFalse(WhiteQueen.CanAttack(BlackQueen));
end;

{$ENDREGION}

initialization
  TDUnitX.RegisterTestFixture(TQueenCreationTests);
  TDUnitX.RegisterTestFixture(TQueenAttackTests);
end.
unit uQueenAttack;

interface

type
  TQueen = class
  private
    x,y:integer;
  public
    function CanAttack(aQuenn:TQueen):boolean;
    constructor Create(const aRow, aCol:integer);
  end;

implementation

uses
  System.SysUtils;

{ TQueen }

function TQueen.CanAttack(aQuenn: TQueen): boolean;
begin
  Result := (x = aQuenn.x) or (y = aQuenn.y) or           // same row,col
            ((x + y) = (aQuenn.x + aQuenn.y)) or          // first + second diagonal
            (Abs(x - y) = Abs(aQuenn.x - aQuenn.y));      // third + four diagonal
end;

constructor TQueen.Create(const aRow, aCol: integer);
begin
  inherited Create;

  if aRow < 0 then
    raise EArgumentException.Create('row not positive');
  if acol < 0 then
    raise EArgumentException.Create('column not positive');
  if (acol > 7)  then
    raise EArgumentException.Create('column not on board');
  if (aRow > 7) then
    raise EArgumentException.Create('row not on board');

  x := aRow;
  y := aCol;
end;

end.

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