interview_practice.md

Practicing Interview Problems

Technical interviews can be stressful, but like most anything else, they are a learned, practiced skill. DON'T PANIC! Technical interviews are not necessarily about evaluating the validity of your solution, but often are more about evaluating a candidate's technical communication skills and problem solving approach.

If you approach problems systematically, and communicate clearly, you'll be most of the way there.

Problem Solving approach

1. Understand the Probem

   • Ask your interviewer questions
   • Draw a picture of what you understand
   • Create a specific example

2. Devise a plan

   • What is the simplest approach that you can think of?
   • Have you solved any similar problems
   • Outline your approach in plain English
   • Draw a picture of your data structure

3. Execute the plan

   • Turn your plain language description into code
   • Write whiteboard code slowly
   • Check each step
   • Ask questions / call out places where you don't know the syntax

4. Check your answer

   • Run examples through your whiteboard code
   • Think about the number of steps that your solution takes
   • Can you improve your solution? Red, Green, Refactor!

Example Problem: Reversing a Linked List

Problem statement: Given a linked list l, write a method reverse that takes l as input and then returns a linked list rev_l which has its values in reverse order. You may mutate the list l.

A linked list is defined via the following class:

class ListItem
  attr_accessor :value, :nxt
  def initialize(val, nxt = nil)
    @value = val
    @nxt  = nxt
  end
end

Each ListItem has a value method which returns the value stored in the list item, and a next method that returns the next ListItem if it exists and nil if that item does not exist.

The solution that we discussed in class was removing the last element from the list repeatedly, and adding the element to a new list. Step through the problem and this (or an alternate solution) using the problem solving framework outlined above.

Is there a better solution?