In this activity, you will model a Stack as a stack of index cards.

Start by creating 3 index cards with the following characters:

1. "{"
2. "["
3. "("

As the examples get more complex, you will need to create more index cards when you have multiple of the same character.

Run the check_it.rb file. For each of the examples provided at the end of the file:

1. Every time the Stack#push method is called, put that character on top of the Stack.
2. Every time the Stack#pop method is called, remove the top index card from the Stack.

After you have looked at all examples, answer the following questions:

• What is the check_it algorithm checking?
• What other applications could this algorithm have?
• What kinds of problems are Stacks good at?

Implement the following methods for the Stack class (be sure to use TDD):

• search(element) - search for element and return its index, or nil if not found
• peek - return, but don't remove, the top element
• clear - clear the Stack
• empty? - return a boolean indicating if there are any elements in the stack