Suppose you have a web form that allows users to upload JPG, GIF or PNG images. Before you store the images in your system, you want to convert them all to the JPG format. Design an image converter API. Sketch out all classes and interfaces that are involved.

Note: the actual code necessary to convert a JPG image to a GIF image is not the point. Just place a comment at the appropriate location where the actual conversion should occur.

Suppose you have an array of 99 numbers. The array contains the digits 1 to 100 with one digit missing. Describe four different algorithms to compute the missing number. Two of these should optimize for low storage and two of these should optimize for fast processing.

Define the following object oriented concepts:

• Class, object (and the difference between the two)
• Instantiation
• Method (as opposed to, say, a C function)
• Static methods and classes
• Destructor/finalizer
• Inheritance
• Encapsulation
• Multiple inheritance (and give an example)
• Abstract class
• Interface/protocol (and different from abstract class)
• Method overriding
• Method overloading (and difference from overriding)
• Polymorphism (without resorting to examples)
• Method visibility (e.g. public/private/other)

Explain big o notation and how it is useful in computer science to classify algorithms.

• What order is a hash table lookup?
• What order is determining if a number is even or odd?
• What order is finding an item in an unsorted list?
• What order is a binary search?

Describe bitwise operators AND, OR, XOR and NOT. Describe how you might use these.

How do these bitwise operators differ from logical operators?

If you have access to a function that returns a random integer from one to five, write another function which returns a random integer from one to seven.

Discuss an algorithm to traverse a tree, depth first.

Construct a regular expression that matches a valid email address.

Efficiently calculate the shortest distance between two Facebook users given an API endpoint that returns all friends of a given user.

Given two arrays of strings, A and B.

B contains every element in A, and has one additional member, for example:

* A = ['dog', 'cat', 'monkey]
* B = ['cat', 'rat', 'dog', 'monkey']

Write a function to find the extra string in B. Do this in O(n)