Problem statement

You need to build an application that gives users a capability to draw shapes on a canvas and edit them.

Create an API (a set of classes and methods) to allow a UI developer to implement the UI for the application described below (you are not in charge of the UI).

1. Add / remove shapes to / from canvas:
   • Rectangle
   • Circle
   • Triangle
2. Shape attributes:
   • Size
   • Color
   • Position
3. Each shape on canvas maybe selected or unselected:
   • Changing attribute(s) on the selected shape should have an immediate effect on the canvas.
   • The API can also batch requests for change before applying them to the canvas.

Please notice that shapes can’t overlap.

Data structures:
Your API and the UI share a 2D array of type int, which represents the drawing canvas (you are responsible to fill it and update it correctly).