# Cracking the coding interview

## The Interview Process

Based on:
- Analytical skills
- Coding skills
- Technical knowledge / CS fundamentals
- Culture fit / Communication skills

Why:
- False negatives are acceptable (better miss a good candidate than selecting a bad candidate).
- Problem solving skills are valuable (if you can solve, you are probably smart).
- Basic data structure and algorithm knowledge is useful. Problem solving questions almost always involve them.
- Whiteboards let's you focus on the main aspect.
- It is not for everyone, but is a reasonable judgement.

Question selection:
- Every interviewer selects their own question
- Often don't differ much from asked recently or three years ago by whichever company, pretty much the same.
- Performance of candidate is relative to another candidate.

FAQ:
- Check in within 3 - 5 days with your recruiter after interview (if you haven't heard from them yet).
- Late response does not say anything about your status of getting hired (or not).
- Almost always you can reapply, with period of 6 months to 1 year.

## Behind the Scenes

Recruiter:
- As recruiter beforehand the position of the interviewer (Engineer usually performs technical interview).
- Often the interviewer does not decide if you get hired.

Screening often involves:
- coding, algorithm questions
- behavioral questions
- design/architecture
- often 3 to 6 in-person interviews (with lunch: good time to discuss culture).

The Microsoft Interview:
- Your recruiter can help you.
- Often 4 to 5 meetings, with different teams.
- Speaking with the hiring manager is a good sign.
- Recruiter not responsive? probably busy.
- Question(s): Why do you want to work for Microsoft?
- Show that you are passionate;
- "I've been using Microsoft software as long as I can remember, and I'm really impressed at how Microsoft manages to create a product that is universally excellent. For example, I've been using Visual Studio recently to learn game programming, and its APls are excellent."

The Amazon Interview:
- Often 1 to 2 to more phone meetings, with a specific team.
- Write code via shared editor.
- Broad set of questions to see what you are familiar with.
- Fly to Seattle (or whichever you are applying for) for 4 to 5 in-person interviews.
- Code on a whiteboard.
- Doing bad in an interview is relative; if you are wrong does not mean you won't pass.
- Impress hiring manager & bar raiser (from different team).
- Questions: Scalability & OO-design.
- Prepare for scalability questions.

The Google Interview:
- Often 1 phone meeting, technical questions, sometimes with shared document. Often not strong factor.
- Same questions on phone as on-site interviews.
- Interview with 4 to 6 people, one is lunch interviewer (often great time to ask honest questions).
- Each interviewer can conduct interview however (s)he likes.
- An enthusiatic interviewer is important for getting hired.
- Can take several weeks (so many stages and committees).
- Questions: Analytical Ability, Coding, Experience and Communication.
- Prepare for system design and scalability.

The Apple Interview:
- Often 1 phone screen interview to get a basic sense of skills.
- 6 to 8 interviews with members of team and key people.
- Mix of one-on-one, two-on-one.
- Be ready to code on whiteboard. Communicate your thoughts clearly.
- Lunch interview appears casual but is still interview.
- Interview with director and VP is good signal.
- Questions: read up on the product.
- What could be improved?
- Show passion for Apple products.

The Facebook Interview:
- Often 1 to 2 phone screen interviews. It will be technical and involve coding, usually with online document editor.
- Homework assignment which is a mix of coding and algorithms.
- Pay attention to coding style.
- On-site primarily interview with other software engineers. Hiring managers often involved.
- Roles:
- Behavioral ("Jedi"): Successful in Facebook's environment? Culture and values, excited/passionate, tackle challenges, interest in Facebook?
- Coding and Algorithms ("Ninja"): Standard questions.
- Design/Architecture ("Pirate"): Discuss trade-offs and solutions.
- Often two "Ninja" and one "Jedi"; Experienced also get "Pirate".
- Questions: Entrepreneurial spirit; Show that you love to build stuff fast.
- Show that you can build elegant and scalable solution.
- Have a 6 week bootcamp; senior dev mentorship, learn best practices, get greater flexibility in choosing a project.

The Palantir Interview:
- Interviews for a specific team.
- Often 2 phone interviews; 30 to 45 minutes; primarily technical. Heavy focus on algorithms.
- Get send HackerRank coding assessment.
- On-site interview with up to five people.
- Show passion for the company. Often harder questions that Google.
- Questions: prior experience, domain knowledge, DS and Algo, Design.

## Special Situations

Experienced candidates:
- Algorithms will always be important
- professionally: more focus on system design and architecture

Testers and SDETs:
- How would you test it
- Know your coding
- Antying can be tested
- Behavioral is also important

Career advice:
- Coding skills are key
- Don't think you can switch from easy to hard job

Product (and Program) Management
- Handle ambiguity
- Ask a lot of questions
- Focus on customer (Attitude, Technical Skills)
- Multi-Level communication (All levels in company hierarchy)
- Passion
- Teamwork / Leadership

Dev Lead and Managers
- Be strong with coding and algorithms
- Teamwork / Leadership
- Prioritization
- Communication
- "Getting Things Done" (Motivate people and finish stuff)

Startups
- Can be very different from one to the next
- Often get in through personal reference
- Often not able to sponsor visa
- You need to be entrepreneurial ("Hit the ground running")
- Personality, Skill set and Experience fit

Acquisitions and Acquihires:
- Not always easy way to "get in"

For Interviewers
- Don't ask questions in this book
- Ask Medium and Hard Problems
- Look for questions with multiple hurdles, insights or optimizations
- Hard questions not hard knowledge
- Avoid "scary" questions
- Probe deeper for behavioral questions
- Coach candidates
- Give them silence
- Modes of questioning:
- Sanity Check: Minimum degree of competence
- Quality Check: Rigorous questions designed to make the candidate think
- Specialist Questions: Specific topic
- Proxy Knowledge: Ask question related to their experience

## Before the Interview
Getting the Right Experience:
- Take the Big Project Classes
- Get an Internship
- Start Something
- Shift Work Responibilities More Towards Coding
- Use Your Nights and Weekends

Write a Great Resume:
- Length of 1.5 to 2 pages
- Limit to most impressive items

Employment History:
- Write Strong Bullets (SMART principle)

Projects:
- Only show most important 2 to 4 projects

Programming Languages and Software:
- Almost always leave out Microsoft Office
- No IDE
- Best first with your expert level

Advice for Non-Native English Speakers and Internationals
- Proofread for typo's
- Leave out age, marital status and nationality

Beware of (Potential) Stigma
- Enterprise language (.NET etc.)
- Don't mention specific "Java"-versions (or other programming language specific versions etc.)
- Don't mention too much (irrelevant) technologies
- Know more than One or Two "Similar" languages (Like C# & .NET or Ruby & Python)

Preparation Map
- See this how to prepare

## Behavioral Questions

Common questions about projects you've done:
- Challenges
- Mistakes/Failures
- Enjoyed
- Leadership
- Conflicts
- What You'd Do Differently

Should elaborate on projects where I've had a central role.

What are your weaknesses?
- Perfectionist; prematurely optimize. Can be detrimental to speed.
- ...

Questions for interviewer:
- What brought you here? What was most challenging for you?
- What is ratio of testers to developers? What is interaction like? How does project planning happen on the team?
- I noticed that you use technology X. How do you handle problem Y?
- What opportunities are there in this company to learn X?
- I'm not familiar with technology X, but sounds cool. Could you tell me a little bit more about that?

Asnwering:
- Limit details; "I can co into more details if you like"
- Focus on your own impact
- give nugget (what will I tell) first and then S.A.R. response

So, tell me about yourself...
- Current role (I'm an .... at .. where I was responsible for ...)
- College
- Post college
- Current role details
- Outside work
- Wrap up

## Big O

Examples of runtime:
- O(1) = Constant time
- O(n) = Linear time

Runtime bound types:
- O (big O): Upper bound on time
- Ω (big omega): Lower bound on time
- Θ (big theta): Tight bound on time

Interview: provide tightest runtime description.

Best case (best time), Worst case (worst time) and expected case (average time) describe big O (or big theta) time for particular inputs or scenarios.

Space and Time complexity:
- array of n will take O(n) space and time complexity.
- Drop constants (O(2N) becomes O(N))
- Drop non dominant terms (O(N^2 + N) becomes O(N^2))
- Don't drop when terms with different variables (O(B^2 + A) stays O(B^2 + A))
- Addition or multiplication:
- Two for loops consequtively = O(A + B)
- Two for loops nested = O(A * B)