How to Pass Google Phone Screen

Introduction

A few years ago, I managed to successfully pass the Google online coding test. It was extremely challenging. In this blog, I explain how I prepared for it.

Purpose of the Coding Test

The purpose of the online coding test is to identify candidates who may do well on the onsite interview. It basically measures how good problem solver, coder you are.

Exam / Test

You can use most of the popular programming languages (like Java, C++, Python, Ruby…). You will be talking to an interviewer throughout the test. Test usually last for about an hour. Given the time spend for introductions, coding part lasts for about 45 minutes.

Through out the exam you will be talking to an interviewer. Usually he would start with an simple coding question then add more and more complexity to it as you progress. You will be using google docs for coding.

Preparation

Brush up your knowledge on data structures and algorithms. Cover all basics.

Data Structures

• Stack
• LinkedList
• Queue
• Arrays
• Heap
• Binary Search Trees
• Hashing

Algorithms

• Sorts – Merge Sort, Quick Sort, Heap Sort, Topological Sort
• Search – Binary Search
• Tree Traversals – DFS, BFS, Inorder, PreOrder and Post Order

Do not waste your time looking at too complex data structures/algorithms. It is very unlikely you will get a complex problem given the time limitations.

Learn to Calculate Time / Memory Complexity

You are usually asked to provide the time/memory complexity of your code.So brush up how to calculate this on a code. Also try to remember time complexity of above classic algorithms.

Recommended Readings

I highly recommend you to invest on Amazon best seller Cracking the Coding Interview: 189 Programming Questions and Solutions book.

This book covers all the algorithms, data structures that needed for your interview. It also covers Time and Memory complexity calculations. It briefly goes through the interview structure of the each big company like Google, Amazon and Facebook. This book also has lot of practice questions with solutions. Book is not cheap. But a very little investment considering that it will help to get in Google.

Practice Practice Practice

The practice is the key. Do as much as practice questions you can. If you buy above book, you try the practice questions of the book. There are several online web sites like Leetcode which provide practice algorithmic questions. Make the best use of them.

During the Test

Don’t Rush In

Don’t jump into solving problem too quickly. Questions are bit ambiguous; this is on purpose. So discuss the problem, ask questions to clear out any ambiguities you may have.

Think Out Loud

Also keep a good communication with the interviewer. Speak out your thought process. If you can think of several solutions to solve the problem, discuss them with the interviewer. Tell him which is the best solution and why you think it is. Also,  you can access the internet during the exam.

Write Good Code

This is the first time Google is going to see your code. So try to give the best first impression. Follow basics; use meaningful variable/method names, move the redundant code to functions. Try to create classes instead of using complex collections. Try to output the best industrial level software you can.

Do not Brute Force

You may be tempted to solve some problems by brute force. But this will not raise any eyebrows. Try to provide a code that can do better than the Brute Force.

Finally

Personally, I took about 3 weeks to prepare my self for the coding test. So start early.

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How to Pass Google Phone Interview

Introduction

A few years ago, I managed to successfully pass the Google online coding test. It was extremely challenging. In this blog, I explain how I prepared for it.

Purpose of the Coding Test

The purpose of the online coding test is to identify candidates who may do well on the onsite interview. It basically measures how good problem solver, coder you are.

Exam / Test

You can use most of the popular programming languages (like Java, C++, Python, Ruby…). You will be talking to an interviewer throughout the test. Test usually last for about an hour. Given the time spend for introductions, coding part lasts for about 45 minutes.

Through out the exam you will be talking to an interviewer. Usually he would start with an simple coding question then add more and more complexity to it as you progress. You will be using google docs for coding.

Preparation

Brush up your knowledge on data structures and algorithms. Cover all basics.

Data Structures

• Stack
• LinkedList
• Queue
• Arrays
• Heap
• Binary Search Trees
• Hashing

Algorithms

• Sorts – Merge Sort, Quick Sort, Heap Sort, Topological Sort
• Search – Binary Search
• Tree Traversals – DFS, BFS, Inorder, PreOrder and Post Order

Do not waste your time looking at too complex data structures/algorithms. It is very unlikely you will get a complex problem given the time limitations.

Learn to Calculate Time / Memory Complexity

You are usually asked to provide the time/memory complexity of your code.So brush up how to calculate this on a code. Also try to remember time complexity of above classic algorithms.

Recommended Readings

I highly recommend you to invest on Amazon best seller Cracking the Coding Interview: 189 Programming Questions and Solutions book.

This book covers all the algorithms, data structures that needed for your interview. It also covers Time and Memory complexity calculations. It briefly goes through the interview structure of the each big company like Google, Amazon and Facebook. This book also has lot of practice questions with solutions. Book is not cheap. But a very little investment considering that it will help to get in Google.

Practice Practice Practice

The practice is the key. Do as much as practice questions you can. If you buy above book, you try the practice questions of the book. There are several online web sites like Leetcode which provide practice algorithmic questions. Make the best use of them.

During the Test

Don’t Rush In

Don’t jump into solving problem too quickly. Questions are bit ambiguous; this is on purpose. So discuss the problem, ask questions to clear out any ambiguities you may have.

Think Out Loud

Also keep a good communication with the interviewer. Speak out your thought process. If you can think of several solutions to solve the problem, discuss them with the interviewer. Tell him which is the best solution and why you think it is. Also,  you can access the internet during the exam.

Write Good Code

This is the first time Google is going to see your code. So try to give the best first impression. Follow basics; use meaningful variable/method names, move the redundant code to functions. Try to create classes instead of using complex collections. Try to output the best industrial level software you can.

Do not Brute Force

You may be tempted to solve some problems by brute force. But this will not raise any eyebrows. Try to provide a code that can do better than the Brute Force.

Finally

Personally, I took about 3 weeks to prepare my self for the coding test. So start early.

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How to Pass Amazon Online Coding Test

Introduction

Recently, I was able successfully to pass the Amazon Online Coding test. I was an amazing experience that pushed my mental strengths to the limit. In this blog, I am going to explain what did I do to successfully pass the test. Let’s start with the test structure.

Test Structure

The purpose of the online coding test is to identify candidates who may do well on the onsite interview. It measures the problem solving skills and coding skills of the applicant. Also it has some questions to measure you against Amazon Leadership Principals. You’d be taking the test on a online code pad tool. You can use most of the popular programming languages. You can go to the tool and get familiar with the features before attempting the exam.

Test has two coding questions. First question is easier than the second. You will have 90 mins to complete both questions. Once you’ve submitted the code, you will get some MCQ questions about Leadership Principals. These questions is not timed, you can take as much as time you like.

Preparations

Let’s see how to prepare for the tests. Brush up your knowledge on basic data structures like Stack, Linked List, Queue, Heap, Binary Search Trees, Hash Tables and Graphs. Sorting and searching are the most popular questions in test. So brush up your knowledge on Merge Sort, Quick Sort, Heap Sort, Binary Search.

Tree traversals are also important. Read up on DFS and BFS. Cover all three traversal models pre Order, in Order and Post order. Study Prim’s and Dijkstra’s algorithms for graph traversal. Also read about Divide and Conquer and Dynamic Programming.

You usually asked to provide the time/memory complexity of your code. So study how to calculate it. Also try to remember time complexity of classical algorithms.

Recommended Readings

You could study by your self. But I highly recommend you to invest on Amazon best seller Cracking the Coding Interview: 189 Programming Questions and Solutions book.

This book covers algorithms, data structures needed for the test. It explains how to compute time and memory complexities. Very importantly it has 189 practice questions. Book is not cheap. But a sound investment considering that it will help to get to Amazon.

Looking for a free book??

If above book is too expensive, an alternative book is Coding Interview Questions. You can read this book for free for 30 days if you register for Amazon’s Kindle Unlimited Membership Plan’s free trial period. You don’t even have to have a Kindle. Just log in to read.amazon.com and start reading.

Practice Practice Practice

Practice is the key. Do as much as practice questions you can. Try the practice questions of the book if you have it. Also there are several online web sites (like Leetcode) which provide hundreds of practice algorithmic questions. Make the best use of them.

During the Exam

You can access the internet during the exam. You are allowed to use your own IDE. But the risk is if you couldn’t copy paste your code on time, you will loose everything.

Time is Precious

50% of the exam is about time management. Two questions are hard enough to make it difficult to finish both within 90 minutes. If the first question is the easier one, don’t waste too much time on it.

If you are running out of time, prioritize the important bits of the algorithm. For example, if you are going to implement a sort, you should prioritize the Comparator since it’s going to be to the core logic of the program. To have any chance to pass the interview, you should at least have something to show for, for both questions.

Write Good Code

This is the first time Amazon is going to see your code. So give the best first impression. Follow basics; use meaningful variable/method names, move the redundant code to functions. Try to create classes instead of using complex collections. Write comments where needed. Try to output the best industrial software you can.

Do not Brute Force

You may be tempted to solve problems by brute force. But this is highly dicoraged. Try to provide a optimal solution than the Brute Force. Having 60% completed code of the optimal solution is better than a 100% working code of the  brute force solution.

Leadership Questions

After coding questions, you will have to answer a questionnaire which evaluates whether you are a good cultural fit for Amazon. Try to be your self and answer honestly. If you and company are not going to be a good match, it’s going to be a bad move for both the parties.

Finally

Don’t trust the tool too much save your work continuously as you progress. I took about 3 weeks to prepare my self for the coding test. Try to start early as possible.

Finally Good luck!!!

 

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What are SOLID Principles?

Follow SOLID Principals

SOLID principles are widely accepted set of rules that let you design/implement reusable and flexible Classes and methods. They consist of the following five principles.

Single Responsibility Principal – Promotes Encapsulation

A class/method should have a single, well-defined functionality. They should only contain code responsible to a single actor (of a use case).

Classes and Methods change because the requirements of the actors change. If a class / a method only contain code that is responsible for a single actor, they only have only one reason to change. This is important because different actors have different requirements, which evolves in different phases and for different reasons.

Open Closed Principal – Promotes Abstraction + Polymorphism

Classes (even Systems) you develop should be open for extension and closed for modification. New functionalities should introduce new codes to a system, not changes to the existing code. The modules you design should never change. When requirement changes you should extend and add more modules to change the behavior of the system.

This principle promotes Abstraction and Polymorphism. Your module should be designed on top of immutable abstractions so it never changes. However, anyone can implement different derivations of these abstractions to introduce new behaviors to the system.

Things that change for different reasons and in different rates, should exist in different places in the code. It is impossible to make a system 100% agnostic for all changes. The designer should find the most probable changes and should make the system to be resilient against them.

Find this very interesting paper on the topic – link.

Liskov Substitution Principal – Abstraction and Hierarchy

Any subtype should be directly substituted in place of a supertype reference. This means that a reference of the supertype should be replaceable with a subtype object without breaking the program. For this principle to work, it is essential that subtype does not change the behavior of supertype. The subtype should provide all the features of the supertype, then some extra

Find the research paper here.

Interface Segregation Principle

A client should not be forced to depend on the method that it does not need. This principle enforces splitting large interfaces to several small interfaces.

Dependency Inversion Principle

Abstract modules should contain high-level business logic. Concrete implementations should contain implementation details. When a high-level module needs to call a low-level module, define an interface on the side of the high-level module to invert the dependency.

 

 

Install Ubuntu Mate in Raspberry PI using Mac and no Keyboard

Introduction

In this blog, I am going to explain how you can install your Raspberry PI using a mac and without any keyboards. Also, you need minimal technical knowledge to do so. You will need a mouse and a display device. So here it goes.

Step 1 – Download Ubuntu Mate

Get it from the following link. Then extract it to get the .img file.

https://ubuntu-mate.org/raspberry-pi/

Step 2 – Plug Micro SD card to your Mac

Connect your Micro USB card to the mac. If your mac is a new (fancy) one with only Thunderbolt ports you can buy a micro SD card adapter from Amazon for a couple of bucks.

Step 3 – Find the Device Identifier

Mac will auto-mount your micro sd card. Go to the Disk Utility, select your SD card. Note the disk identifier of your card. For my case, it is disk4. Then unmount your disk (do not Eject).

Step 4 – Write Ubuntu Mate image to the SD card

Here is the command you should execute.

sudo dd bs=1m if=path_of_your_image.img of=identifier_of_your_disk conv=sync

For my case, here is the exact command I had to run.

sudo dd bs=1m if=~/downloads/ubuntu-mate-16.04.2-desktop-armhf-raspberry-pi.img of=/dev/disk4 conv=sync

This command takes some time to complete, so stay put.

Step 5 – Boot your Raspberry

Plugin the micro sd. You need to connect a mouse and display to it as well. Turn on the raspberry and boot it up.

Step 6 – Set up username/password without a Keyboard

When it boots up it will ask you to give a login and a password. But you can’t do it because you don’t have a keyboard. The trick is to copy any text from the window and paste it on the login and password text boxes. For this example, I used “computer” username and “computercomputer” as the password. Set it up, you are good to go.

Step 7 – Enable On Screen Keyboard

Go to Applications–> Universal Access –> Onboard

Hope this helps. Refer this blog to see how you can set up Ubuntu Mate after installation for programming.