cracking the coding interview nitish upreti. nitish upreti @nitish
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CRACKING THE CODING INTERVIEW
Nitish Upreti
Why this Talk?Why should you care ?
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 ?
Or Not ?
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?
Preparations Matter!“Sweat now so you don't bleed later.”
Take Away….
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 ( N2 )
Can we do better?At Google’s scale there will be Billion Numbers !
Sorting + Binary Search ?
O (N log N) + O (log N)
Can we do Even Better?
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 !
Complexity ?Time : O ( N )Space : O ( N )
MUST READ Books …
Before I Finish …
GSoC 2014 Is On!
Feedback / Questions ?
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