CRACKING THE CODING
INTERVIEW
Nitish Upreti

Feedback Please !
( I am a Data Junkie… ) www.meet.ps

For the love of Computer Science
…

Building Amazing Products

Working with the best of
People …

Have an Impact !

Head start in Building your career …

Money & Free Food ?

Start Your own Company ?

Working for the Top
Technology Companies.
(Computer Science-Engineering majors are most pampered and well paid…)

Easy : Just clear the coding interview ?

Some of us are scared !
How does the interview work?
What do they judge me on?
Do’s / Don’ts

Are these interviews fair?
Can you judge someone in few hours or a day?

Think of Interviews as acing SATs /
GREs …
( Whether they are any good is debatable!)

GAME PLAN
1.
Study all my subjects well.
:
2.
Finish all Assignments/Projects.
3.
Get an awesome GPA.

There is more to it …

Would you practice for a Sprint by running marathons each day?

Take Away….
Preparations Matter!
“Sweat now so you don't bleed later.
”

Lets get cracking!

Before the Interview…

How to get interviews at the first place?
• Career fairs.
• Referrals from friends and seniors. (Almost guarantees an interview)
• Be active on LinkedIn.
• Visit Hackathons.
• Start competing on HackerRank / TopCoder.
• Email cto_first_name / ceo_first_name @startup

Quick Preliminaries
• Perfect your resume
(No spelling mistakes / grammar errors)
ACM provides help!
• Prepare Behavioral Questions
Judging You On :
What you learned?
Most Challenging Problems ?
Most Interesting Problem ?
Hardest Bug ?
Enjoyed Most ?
Conflict with Teammates ?

So I got the call 

How does the Interview Process work ?
( At least for the Popular Ones …. )

Interview Process
• Starts with an Email Conversation.
• Scheduling day/time for Phone or Campus screening
• Internships : Usually 2 telephonic rounds.
• Full time : 5-7 interviews
• PSU Microsoft experience is an exception when it comes to interviews. (Why?)
• You are notified in a couple of weeks.
• Details are in the Book!

How should I prepare ?

White Board Coding ….
(Without the cozy compiler : Marathon and
Sprint metaphor again!)

What should I prepare?

Almost Comprehensive List
…
• Elementary DS :
– Arrays, Stacks & Queues
– Linked Lists
– Trees ( Binary Trees, Binary Search Trees)
– Hash Tables
• Asymptotic Analysis
• Sorting with their Runtimes.
• Recursion !
• String Problems
• Good to know : TRIE and Priority Queue (
BinaryHeap)

Advanced
• Divide and Conquer Algorithms.
• Greedy Algorithms
• Dynamic Programming
• Graph Algorithms
• Some Design Problems

During the Interview …

Key things to keep in mind
• All questions are language independent.
• Start Talking ( Interviewers nudge you towards the right direction )
• Think before you start / Don’t rush.
• Propose a variety of solutions idea before settling on coding a particular idea.
• Sound Enthusiastic !
• Ask questions in the end : How do you work?
What do you work on?

Make Or Break it !
• Think about Corner cases.
• Test your code once your done.
• Be Space / Time Efficient.
( Distinguishes a Good Vs Bad Interview)

Lets dissect a real interview question !

Given a set of integers, is there a subset of size k whose sum is zero?
Array = { 3, 9, 1 , 6 , 0, 2 }
Sum = 8

I am STUMPED !

Let us start talking ….

Brute Force Anyone ?
Find all the possible sums and if the given sum is one of them, we have a solution!
Brute Force could be a good start.
Don’t code it yet !

Runtime Analysis ?
O ( N 2 )

Can we do better?
At Google’s scale there will be
Billion Numbers !

Sorting + Binary Search ?
O (N log N) + O (log N)

How about a Hash Table
Solution?
First Passes :
Create a Map (HashMap)
Array = { 3, 9, 1 , 6 , 0, 2 }
Hash = { (3,T) (9,T) (1,T) (6,T)
(0,T)(2,T) }
Scan through the keys & look for remainder.

Corner Case : Duplicate Elements !
Array = { 3, 9, 1 , 6 , 0, 4 }
Hash = { (3,T) (9,T) (1,T) (6,T)
(0,T)(4,T) }
Solution : Store Count !

Time : O ( N )
Space : O ( N )

MUST READ Books …

Before I Finish …

GSoC 2014 Is On!

Feedback / Questions ?