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artemkorsakov's solution

to Queen Attack in the C# Track

Published at Apr 21 2019 · 0 comments
Instructions
Test suite
Solution

Note:

This exercise has changed since this solution was written.

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.

Running the tests

To run the tests, run the command dotnet test from within the exercise directory.

Initially, only the first test will be enabled. This is to encourage you to solve the exercise one step at a time. Once you get the first test passing, remove the Skip property from the next test and work on getting that test passing. Once none of the tests are skipped and they are all passing, you can submit your solution using exercism submit QueenAttack.cs

Further information

For more detailed information about the C# track, including how to get help if you're having trouble, please visit the exercism.io C# language page.

Source

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

QueenAttackTest.cs

// This file was auto-generated based on version 2.2.0 of the canonical data.

using System;
using Xunit;

public class QueenAttackTest
{
    [Fact]
    public void Queen_with_a_valid_position()
    {
        var actual = QueenAttack.Create(2, 2);
    }

    [Fact(Skip = "Remove to run test")]
    public void Queen_must_have_positive_row()
    {
        Assert.Throws<ArgumentOutOfRangeException>(() => QueenAttack.Create(-2, 2));
    }

    [Fact(Skip = "Remove to run test")]
    public void Queen_must_have_row_on_board()
    {
        Assert.Throws<ArgumentOutOfRangeException>(() => QueenAttack.Create(8, 4));
    }

    [Fact(Skip = "Remove to run test")]
    public void Queen_must_have_positive_column()
    {
        Assert.Throws<ArgumentOutOfRangeException>(() => QueenAttack.Create(2, -2));
    }

    [Fact(Skip = "Remove to run test")]
    public void Queen_must_have_column_on_board()
    {
        Assert.Throws<ArgumentOutOfRangeException>(() => QueenAttack.Create(4, 8));
    }

    [Fact(Skip = "Remove to run test")]
    public void Can_not_attack()
    {
        var whiteQueen = QueenAttack.Create(2,4);
        var blackQueen = QueenAttack.Create(6,6);
        Assert.False(QueenAttack.CanAttack(whiteQueen, blackQueen));
    }

    [Fact(Skip = "Remove to run test")]
    public void Can_attack_on_same_row()
    {
        var whiteQueen = QueenAttack.Create(2,4);
        var blackQueen = QueenAttack.Create(2,6);
        Assert.True(QueenAttack.CanAttack(whiteQueen, blackQueen));
    }

    [Fact(Skip = "Remove to run test")]
    public void Can_attack_on_same_column()
    {
        var whiteQueen = QueenAttack.Create(4,5);
        var blackQueen = QueenAttack.Create(2,5);
        Assert.True(QueenAttack.CanAttack(whiteQueen, blackQueen));
    }

    [Fact(Skip = "Remove to run test")]
    public void Can_attack_on_first_diagonal()
    {
        var whiteQueen = QueenAttack.Create(2,2);
        var blackQueen = QueenAttack.Create(0,4);
        Assert.True(QueenAttack.CanAttack(whiteQueen, blackQueen));
    }

    [Fact(Skip = "Remove to run test")]
    public void Can_attack_on_second_diagonal()
    {
        var whiteQueen = QueenAttack.Create(2,2);
        var blackQueen = QueenAttack.Create(3,1);
        Assert.True(QueenAttack.CanAttack(whiteQueen, blackQueen));
    }

    [Fact(Skip = "Remove to run test")]
    public void Can_attack_on_third_diagonal()
    {
        var whiteQueen = QueenAttack.Create(2,2);
        var blackQueen = QueenAttack.Create(1,1);
        Assert.True(QueenAttack.CanAttack(whiteQueen, blackQueen));
    }

    [Fact(Skip = "Remove to run test")]
    public void Can_attack_on_fourth_diagonal()
    {
        var whiteQueen = QueenAttack.Create(2,2);
        var blackQueen = QueenAttack.Create(5,5);
        Assert.True(QueenAttack.CanAttack(whiteQueen, blackQueen));
    }
}
using System;

public class Queen
{
    public Queen(int row, int column)
    {
        if (row < 0)
        {
            throw new ArgumentOutOfRangeException("Queen position must have positive row.");
        }
        if (row > 7)
        {
            throw new ArgumentOutOfRangeException("Queen position must have row <= 7.");
        }
        if (column < 0)
        {
            throw new ArgumentOutOfRangeException("Queen position must have positive column.");
        }
        if (column > 7)
        {
            throw new ArgumentOutOfRangeException("Queen position must have column <= 7.");
        }
        Row = row;
        Column = column;
    }

    public int Row { get; }
    public int Column { get; }

    public override bool Equals(object obj) => obj is Queen queen &&
               Row == queen.Row &&
               Column == queen.Column;

    public override int GetHashCode() => HashCode.Combine(Row, Column);
}

public static class QueenAttack
{
    public static Queen Create(int row, int column) => new Queen(row, column);

    public static bool CanAttack(Queen white, Queen black) => IsSameRow(white, black) ||
               IsSameColumn(white, black) ||
               IsSameDiagonalTopLeftBottomRight(white, black) ||
               IsSameDiagonalBottomLeftTopRight(white, black);

    private static bool IsSameRow(Queen white, Queen black) => white.Row == black.Row;
    private static bool IsSameColumn(Queen white, Queen black) => white.Column == black.Column;
    private static bool IsSameDiagonalTopLeftBottomRight(Queen white, Queen black) =>
        (white.Row - white.Column) == (black.Row - black.Column);
    private static bool IsSameDiagonalBottomLeftTopRight(Queen white, Queen black) =>
        (white.Row + white.Column) == (black.Row + black.Column);
}

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