# Sortable Shapes

Description:

Although shapes can be very different by nature, they can be sorted by the size of their area.

Create different shapes that can be part of a sortable list. The sort order is based on the size of their respective areas:

The area of a Square is the square of its side
The area of a Rectangle is width multiplied by height
The area of a Triangle is base multiplied by height divided by 2
The area of a Circle is the square of its radius multiplied by π
The area of a CustomShape is given

The default sort order of a list of shapes is ascending on area size:

var side = 1.1234D;
var radius = 1.1234D;
var base = 5D;
var height = 2D;

var shapes = new List<Shape>{ new Square(side),
new Triangle(base, height) };
shapes.Sort();

• Use the correct π constant for your circle area calculations:

System.Math.PI

And you only have tests cases to base your code on.

using NUnit.Framework;
using System;
using System.Linq;
using System.Collections.Generic;

[TestFixture]
public class ShapesTests
{
[Test]
public void ShapesAreSortableOnArea()
{
// Arrange
double width, height, triangleBase, side, radius, area;
Random random = new Random((int)DateTime.UtcNow.Ticks);

var expected = new List<Shape>();

area = 1.1234;

side = 1.1234;

triangleBase = 5;
height = 2;

height = 3;
triangleBase = 4;

width = 4;

area = 16.1;

var actual = expected.OrderBy(x => random.Next()).ToList();

// Act
actual.Sort();

// Assert
for (var i = 0; i < 5; i++)
Assert.AreEqual(expected[i], actual[i]);
}
}


My answer below was correct I would like it reviewed and if possible refactored or Improved this was a question I got on Codewars.com and my solution passed all tests on the site.

    using System;
using System.Collections.Generic;
using System.Linq;

public class Shape : IComparable<Shape>
{
public double Area { get; set; }

public int CompareTo(Shape other)
{
return this.Area.CompareTo(other.Area);
}

}

public class Square : Shape
{
public Square(double side)
{
Area = side * side;
}
}

public class CustomShape : Shape
{
public CustomShape(double area)
{
Area = area;
}
}

public class Circle : Shape
{
{
Area = (radius * radius) * Math.PI;
}
}

public class Rectangle : Shape
{
public Rectangle(double width , double height)
{
Area = width * height;
}
}

public class Triangle : Shape
{
public Triangle(double Base, double height)
{
Area = (Base * height) / 2;
}
}

• This looks like a kata from Codewars. Please make sure to show what code is yours and what code is from the site.
– Zeta
Feb 8 '17 at 6:17
• This question is from Codewars but @Zeta but this is ALL MY CODE... Feb 8 '17 at 17:27
• No. The test case isn't. Neither is the description. Keep in mind that by posting your question you licence it under CC-BY-SA.
– Zeta
Feb 8 '17 at 18:42

The main thing I see in your solution, is that your derived classes, would need quite a bit of re-factoring if you needed them in a more general sense. I think having each shape with its own parameters and its own getter for the Area property, is much more adaptable:

public class Square : Shape
{
public double side { get; set; }
public double Area
{
get { return side * side; }
}
public Square(double side)
{
this.side = side;
}
}

• The principle is good, but to nitpick coding conventions: in C# the property should have an initial capital: Side. Feb 8 '17 at 11:11

Your hierarchy presumes that every descendant class will call Area setter. That's wishful thinking. :) You will get away with it in this small exercise, but you wont in more complex projects.

You should make Area abstract.

public abstract class ShapeBase : IComparable<Shape>
{
public abstract double Area { get; }

public int CompareTo(Shape other)
{
return this.Area.CompareTo(other.Area);
}
}


This will enforce every descendant to override it. Note, that there is no public setter. It should not be possible to execute this code:

new Circle(1) { Area = 200000 };


Also, you should normally override equality methods if you implement IComparable<T>. If CompareTo returns 0, Equals should not return false.

• does that mean I have to override all of equality then Feb 8 '17 at 17:26
• @GringoJaimes, you have to override Object.Equals(), IEquatable<T>.Equals() and Object.GetHashCode(). Alternatively you can implement stand-alone IComparer<T>. Then you don't have to do all that. Feb 9 '17 at 7:39