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High 50 Programming Interview Questions with Solutions for 1 to three Years Skilled

For the previous few years, telephone interviews also referred to as the telephonic spherical is the one hottest option to display screen candidates in a programming job interview. It is easy for each events to gauge one another, the candidate does not have to journey to the possible Employer’s premises and the Interviewer additionally does not have to make any essential preparations. That is the second a part of my article on programming interview questions, within the first half, I obtained suggestions that it’s a little bit heavy on coding-based questions and lots of programmers requested me to share the same listing for the telephonic spherical of programming Interviews. With a purpose to clear the telephonic spherical and proceed to the subsequent spherical, you should be adequate to reply all of the questions associated to your Job description.

In a lot of the telephone interviews for Java or C++ builders, you’ll not solely discover questions from respective programming languages but additionally from different know-how like SQL, XML, UNIX, Normal Programming,
Object-oriented programming, Knowledge Construction, and Algorithm, Networking, Coding, and different areas of labor.

Due to this huge nature of the telephone spherical of programming job interviews, it’s essential provide you with a particular technique to current your self in a way Interviewer is anticipating.

Additionally, fundamental information of important knowledge construction and algorithms can also be crucial and that is why I recommend all Java programmers be a part of these on-line Knowledge buildings and Algorithms programs to enhance their information and algorithms expertise.

One of the necessary issues to recollect, whereas answering questions on a telephone interview is to say key factors early and all the time give the purpose reply. Since most interviewers wish to cowl plenty of subjects to display screen the candidate, they normally like to-the-point solutions slightly than blah blah and OK I do know the stuff, you’ll get your probability to elucidate issues in deep within the head to head interview.

By the way in which, this isn’t the arduous and quick rule and you’ll really perceive what the interviewer is anticipating from you by noting his response to your solutions. If he asks follow-up or expects you to talk extra then go forward, nevertheless it rapidly jumps to the subsequent query then be clear and concise.

On this article, I’m sharing some well-liked and fascinating programming questions particularly tailor-made for telephone interviews. Most of them are literally from the telephonic spherical of assorted tech corporations together with banks like Barclays, Citi, Nomura, and varied service-based corporations like Infosys, TCS, CTS, Tech Mahindra, and HCL.

As I discussed earlier than questions are randomly picked from the assorted subjects however principally based mostly upon fundamentals as a result of that’s what the Interviewer assessments on telephone interviews. Although these questions are principally for much less skilled builders like 2 to five years, Senior and skilled programmers can even use these for his or her interview objective.

If you’re significantly getting ready for Job interviews, I additionally recommend you check out both Programming Interviews Uncovered by Wrox or Cracking the coding Interview, two of the great books I’ve discovered for getting ready any programming job interviews.

The primary one is my favourite and I’ve learn it nearly 7 years again, however nonetheless, it is fairly related due to a superb rationalization of information construction and algorithm questions. If you’re an interviewer, you can too use these inquiries to rapidly display screen candidates for improvement positions. I’ve supplied the brief reply right here and a pointer for a extra detailed reply.

High 50 Programming Questions for Telephonic Interviews

Here’s a listing of just about 50 questions from the telephone spherical of programming job interviews. These questions are good for any programmers, builders, software program engineer, QA, and help engineer as a result of they’re based mostly upon fundamentals of programming, however most fitted to programmers and builders.

BTW, If you’re a Java developer and in search of Java Questions for Telephone interviews, take a look at that listing. This listing is extra normal and relevant for all programmers together with Python, Ruby, Perl, and C# builders.

Programming Phone  Interview Questions answers

1. How a lot time does it take to retrieve a component if saved in HashMap, Binary tree, and a Linked listing? the way it change you probably have hundreds of thousands of information?
In HashMap it takes O(1) time, within the binary tree it takes O(logN) the place N is various nodes within the tree and in linked listing it takes O(n) time the place n is various component within the listing. Thousands and thousands of information do not have an effect on the efficiency if the info construction is working as anticipated e.g. HashMap has no or comparatively much less variety of collision or binary tree is balanced. If that is not the case then their efficiency degrades as various information grows.

2. What’s the distinction between Overriding and Overloading? (detailed reply)
Overriding is resolved at runtime whereas overloading is compile time. Additionally, guidelines of overriding and overloading are totally different, for instance in Java, methodology signature of the overloaded methodology should be totally different than authentic methodology, however within the case of overriding it should be precisely similar as an overriding methodology.

3. What’s the distinction between forking a course of and spawning a thread? 
Once you fork a course of, the brand new course of will run the identical code because the mother or father course of however in numerous reminiscence area, however whenever you spawn a brand new thread in present course of, it simply creates one other unbiased path of execution however share similar reminiscence area.

4. What’s a important part? (reply)
A important part is the a part of a code, which is essential and in multi-threading should be solely modified by any thread. Semaphore or mutex is used to guard important part. In Java, you should use synchronized key phrase or ReentrantLock to guard a important part.

5. What’s the distinction between a price sort and a reference sort? (reply)
A worth sort is a extra optimized sort and all the time immutable e.g. primitive int, lengthy, double and float in Java whereas a reference sort factors to an object, which may be mutable or Immutable. You may as well say that worth sort factors to a price whereas reference sort factors to an object.

6. What’s heap and stack in a course of? (detailed reply)
They’re two separate areas of reminiscence in the identical course of. Speaking about Java, the stack is used to retailer primitive values and reference sort to object however precise object is all the time created in heap. One important distinction between heap and stack is that heap reminiscence is shared by all threads however every thread has their very own stack.

7. What’s revision/model management? (reply)
Model management is software program which is used to retailer code and handle variations of codebase e.g. SVN, CVS, Git, Perforce, and ClearCase. They’re very efficient whereas evaluating code, reviewing code and making a construct from earlier steady model. All skilled improvement use some type of revision or model management software, with out them, you can’t handle code successfully, particularly if 20 builders are engaged on similar code base on the similar time. Model management software performs crucial position to maintain code base constant and resolving code conflicts.

8. What’s a strongly typed programming language? (reply)
In a strongly typed language compiler guarantee sort correctness, for instance, you cannot retailer the quantity in String or vice-versa. Java is a strongly typed language, that is why you could have totally different knowledge sorts e.g. intfloatStringcharboolean and many others. You possibly can solely retailer suitable values in respective sorts. However, weakly typed language do not implement sort checking at compile time they usually tree values based mostly upon context. Python and Perl are two well-liked instance of weakly typed programming language, the place you possibly can retailer a numeric string in quantity sort.

9. Are you able to describe the distinction between legitimate and well-formed XML?
A well-formed XML is the one which has root component and all tags are closed correctly, attributes are outlined correctly, their worth can also be quoted correctly. On one other hand, a sound XML is the one which may be validated towards an XSD file or schema. So it is attainable for an XML to be well-formed however not legitimate as a result of they include tags which might not be allowed by their schema.

10. What’s the distinction between DOM and SAX parser? (detailed reply)
DOM parser is an in-memory parser so it masses entire XML file in reminiscence and create a DOM tree to parse. SAX parser is an occasion based mostly parser, so it parses XML doc based mostly on the occasion acquired e.g. opening tag, closing tag, the beginning of attribute or finish of the attribute. Due to their working methodology, DOM parser isn’t appropriate for giant XML file as they are going to take plenty of area in reminiscence and your course of could run out of reminiscence, SAX is the one which must be used to parse massive information. For small information, DOM is normally a lot sooner than SAX.

11. What’s the relationship between threads and processes? (detailed reply)
A course of can have a number of threads however a thread all the time belongs to a single course of. Two processes can’t share reminiscence area till they’re purposefully doing inter-process communication by way of shared reminiscence however two threads from the identical course of all the time share the identical reminiscence.

12. What’s Immutable class imply? (detailed reply)
A category is alleged to be Immutable if its state can’t be modified as soon as created, for instance, String in Java is immutable. When you create a String say “Java”, you can’t change its content material. Any modification on this string e.g. changing into higher case,  concatenating with one other String will outcome within the new object. An immutable object could be very helpful for concurrent programming as a result of they are often shared between a number of threads with out worrying about synchronization. In reality, the entire mannequin of practical programming is constructed on prime of Immutable objects.

13. Why would you ever wish to create a mock object? (reply)
A mock object could be very helpful to check a person unit in your Software program, in reality, stub and mocks a are a robust software for creating automated unit assessments. Suppose you write a program to show forex conversion charges however you do not have a URL to hook up with, now if you wish to check your code, you should use mock objects. In Java world, there are plenty of frameworks which may create highly effective mock objects for you e.g. Mockito and PowerMock.

14. What’s SQL injection?
SQL injection is a safety vulnerability which permits an intruder to steal knowledge from the system. Any system which takes enter from the consumer and creates SQL question with out validating or sanitizing that enter is susceptible to SQL injection. In such system, an intruder can inject SQL code as a substitute of information to retrieve greater than anticipated knowledge. There are a lot of situations on which delicate data e.g. consumer id, password, and private particulars are stolen by exploiting this vulnerability. In Java, you possibly can keep away from SQL injection through the use of Ready assertion.

15. What’s the distinction between an inside be a part of and a left take part SQL? (reply)
In SQL, there are primarily two sorts of joins, inside be a part of, and outer be a part of. Once more outer joins may be two sorts proper and left outer be a part of. 

The principle distinction between inside be a part of and left be a part of is that within the case of former solely matching information from each tables are chosen whereas within the case of left be a part of, all information from left desk are chosen along with matching information from each tables. 

All the time be careful for queries which have “all” in it, they normally require left be a part of wish to write SQL question to seek out all departments and various workers on it. If you happen to use inside be a part of to unravel this question, you’ll miss empty departments the place nobody works.

16. What does the V in MVC stand for, and what does it signify? (reply)
V stands for View in MVC sample. The view is what consumer sees  like net pages. This can be a crucial design sample of net improvement which relies upon segregation of concern so that every space may be modified with out impacting different areas. 

In Java world, there are many open supply framework which offers an implementation of MVC sample like Struts 2 and Spring MVC
By the way in which, M stands the for mannequin and C stands the for controller. Modes are precise enterprise objects like Consumer, Worker, Order; whereas the controller is used for the routing request to appropriate processor.

17. What’s the distinction between a category and an object? (detailed reply)
A category is a blueprint on which objects are created. A category has code and conduct however an object has each the state and conduct. You can not create an object with out creating a category to characterize its construction. The category can also be used to map an object in reminiscence, in Java, JVM does that for you.

18. What’s loose-coupling?
Unfastened coupling is a fascinating high quality of software program, which permits one a part of the software program to switch with out affecting one other a part of the software program. For instance, in a loosely coupled software program, a change in UI structure shouldn’t have an effect on the back-end class construction.

19. What’s the distinction between composition, aggregation, and affiliation? (detailed reply)
Affiliation means two objects are associated to one another however can exist with out one another, Composition is a type of affiliation the place one object consists of a number of objects, however they solely exists collectively e.g. human physique is the composition of organs, particular person organs can’t reside they solely helpful within the physique. Aggregation is a group of object e.g. metropolis is an aggregation of residents.

20. What’s the distinction between an interface and an summary class? (detailed reply)
That is probably the most classical query of all programming interviews. An interface is the purest type of abstraction with nothing concrete in place whereas an summary class is a mixture of some abstraction and concrete issues. The distinction could differ relying upon language e.g. in Java you possibly can lengthen a number of interface however you possibly can solely lengthen on the summary class. For a extra complete dialogue see the detailed reply.

21. What’s unit testing? (reply)
Unit testing is a option to check particular person unit for his or her performance as a substitute of testing entire software. There are plenty of instruments to do the unit testing in numerous programming language e.g. in Java, you should use JUnit or TestNG to write down unit assessments. It’s usually run robotically through the construct course of or in a steady surroundings like Jenkins.

22. Are you able to describe three totally different sorts of testing that could be carried out on an software earlier than it goes reside?
unit testing, integration testing and smoke testing. Unit testing is used to check particular person models to confirm whether or not they’re working as anticipated, integration testing is finished to confirm whether or not individually examined module can work collectively or not and smoke testing is a option to check whether or not most typical performance of software program is working correctly or not like in a flight reserving web site, you need to be capable to ebook, cancel or change flights.

23. What’s the distinction between iteration and recursion? (detailed reply)
Iteration makes use of a loop to carry out the identical step repeatedly whereas recursion calls the perform itself to do the repetitive process. Many instances recursion end in a transparent and concise answer to a fancy drawback like tower of Hanoi, reversing a linked listing or reversing a String itself. 

One downside of recursion is depth  since recursion shops intermediate outcome within the stack you possibly can solely go as much as a sure depth, after that your program will die with StackOverFlowError, that is why iteration is most popular over recursion in manufacturing code.

24. What’s distinction between & and && operator? (detailed reply)
& is a bitwise operator whereas && is a logical operator. One distinction between & and && is that bitwise operator (&) may be utilized to each integer and boolean however logical operator (&&) can solely be utilized to boolean variables. 

Once you do a & b then AND operator is utilized to every little bit of each integer quantity, whereas within the case of a && b, the second argument could or might not be evaluated, that is why additionally it is often called brief circuit operator, at the very least in Java. I like this query and infrequently requested it to junior or developer and school graduates.

25. What’s the results of 1 XOR 1?
The reply is zero as a result of XOR returns 1 if two operands are distinct and nil if two operands are similar, for instance, 0 XOR 0 can also be zero, however 0 XOR 1 or 1 XOR 0 is all the time 1.

26. How do you get the final digit of an integer? (reply)
Through the use of modulus operator, quantity % 10 returns the final digit of the quantity, for instance, 2345percent10 will return 5 and 567percent10 will return 7.  Equally, division operator can be utilized to eliminate the final digit of  a quantity e.g. 2345/10 will give 234 and 567/10 will return 56. This is a crucial method to know and helpful to unravel issues like quantity palindrome or reversing numbers.

27. What’s test-driven improvement?
Take a look at pushed is among the well-liked improvement methodologies during which assessments are written earlier than writing any perform code. In reality, check drives the construction of your program. Purists by no means wrote a single line of software code with out writing a check for that. It tremendously enhance code high quality and infrequently attributed as a top quality of rockstar builders.

28. What’s the Liskov substitution precept? (reply)
Liskov substitution precept is among the 5 precept launched by Uncle Bob as SOLID design rules. It is the ‘L’ in SOLID. Liskov substitution precept asserts that each subtype ought to be capable to work because the proxy for mother or father sort. 

For instance, if a technique besides object of Guardian class then it ought to work as anticipated if you happen to go an object of the Baby class. 

Any class which can’t stand rather than its mother or father violate LSP or Liskov substitution precept. That is really a tricky query to reply and if you happen to try this you find yourself with creating an excellent impression on the interviewer’s thoughts.

29. What’s the Open closed design precept? (reply)
Open closed is one other precept from SOLID, which asserts {that a} system must be open for extension however closes for modification. This implies if new performance is required in a steady system then your tried and examined code shouldn’t be touched and new performance must be supplied by including new courses solely. 

30. What’s the distinction between a binary tree and a binary search tree?
Binary search tree is an ordered binary tree, the place the worth of all nodes within the left tree are lower than or equal to node and values of all nodes in proper subtree is larger than or equal to the node (e.g. root). It is an necessary knowledge construction and can be utilized to characterize a sorted construction.

31. Are you able to give a sensible instance of a recursive algorithm? (instance)
There are many locations the place recursive algorithm suits e.g. algorithm associated to binary and linked listing. A few examples of a recursive algorithm is reversing String and calculating Fibonacci sequence. Different examples embrace reversing linked listing, tree traversal, and fast type algorithm. 

31. What’s the time complexity of an algorithm?
Time complexity specifies the ratio of time to the enter. It reveals how a lot time an algorithm will take to finish for a given variety of enter. It is approximated valued however sufficient to present you a sign that how your algorithm will carry out if the variety of enter is elevated from 10 to 10 million?

32. What are some necessary variations between a linked listing and an array? (detailed reply)
linked listing and array are two of crucial knowledge construction within the programming world. Probably the most important distinction between them is that array shops its component on the contiguous location whereas linked listing shops its knowledge anyplace in reminiscence. 

This offers linked listing monumental flexibility to broaden itself as a result of reminiscence is all the time scattered. 

It is all the time attainable that you simply would not be capable to create an array to retailer 1M integers however can do through the use of linked listing as a result of area is offered however not as contiguous chunk. All different variations are the results of this reality.

For instance, you possibly can search a component in array with O(1) time if you understand the index however looking will take O(n) time in linked listing. For extra variations see the detailed reply.

33. What’s a few methods to resolve collision within the hash desk? 
linear probing, double hashing, and chaining. In linear probing, if the bucket is already occupied then perform test subsequent bucket linearly till it finds an empty one, whereas in chaining, a number of components are saved in similar bucket location.

34. What’s an everyday expression? (reply)
A daily expression is a option to carry out sample matching on textual content knowledge. It is very highly effective software to seek out one thing like some character in a protracted string e.g. discovering if a ebook incorporates some phrase or not. Virtually all main programming language helps common expression however Perl has been famend for its monumental functionality. 

Java additionally helps Perl-like common expression utilizing java.util.regex package deal. 

You need to use the common expression to test if an e-mail is legitimate or not, if a telephone quantity is legitimate, or if a zipper code is legitimate, and even an SSN quantity is legitimate or not. One of many easiest examples of the common expression is to test if a String is a quantity or not.

35. What’s a stateless system?
A stateless system is a system which does not preserve any inside state. Such system will produce the identical output for similar enter at any level of time. It is all the time simpler to code and optimize a stateless system, so you need to all the time try for one if attainable.

36. Write SQL question to seek out second highest wage in worker desk? (answer)
This is among the basic questions from SQL interviews, the occasion it is fairly previous it’s nonetheless fascinating and has plenty of follow-ups you should use to test the depth of candidate’s information. You could find second highest wage through the use of the correlated and non-correlated subquery. 

You may as well use key phrase’s like TOP or LIMIT if you’re utilizing SQL Server or MySQL, given Interviewer permits you. The only option to discover 2nd highest wage is following:


This question first finds most wage after which exclude that from the listing and once more finds most wage. Clearly second time, it might be second highest wage.

37. Are you able to describe the distinction between correlated and non-correlated subquery? (reply)
In correlated sub-query, the inside question relies upon upon the outer question and executes for every row within the outer question. Whereas non-correlated subquery does not depend on the outer question and may be executed independently. 

Attributable to this cause, former is gradual and later is quick. BTW, correlated subquery has some good functions, certainly one of them is discovering Nth highest wage in Worker desk, as seen on earlier SQL query as properly.

39. How do you discover if a quantity is an influence of two, with out utilizing an arithmetic operator? (answer)
Assume it is a query of utilizing the bitwise operator as quickly as you hear restriction about not allowed to make use of arithmetic operator. If that restriction isn’t in place then you possibly can simply test if a quantity is an influence of two through the use of modulus and division operator. By the utilizing bitwise operator, there’s a good trick to do that.  You need to use following code to test if a quantity if energy of two or not

public static boolean powerOfTwo(int x) {
        return (x & (x - 1)) == 0;

x & (x-1) is a pleasant trick to transform proper most bit to zero if it is on, I discovered from hackers delight ebook.

40. How do you discover a  operating Java course of on UNIX? (command)
You need to use the mixture of ‘ps’ and ‘grep’ command to seek out any course of operating on UNIX machine. Suppose your Java course of has a reputation or any textual content which you should use to match towards simply use following command.

ps -ef | grep "myJavaApp"

ps -e will listing each course of i.e. course of from all consumer not simply you and  ps -f provides you with full particulars together with PID, which shall be required if you wish to examine extra or wish to kill this course of utilizing kill command.

41. How do you discover massive information in UNIX  like greater than 1GB? (command)
You possibly can simply discover large information through the use of the discover command as a result of it offers an possibility to look information based mostly upon their measurement. Use this in case your file system is full and your Java course of is crashing with no more room. This command will listing all information that are greater than 1GB. You possibly can tweak the dimensions simply like to seek out all information with greater than 100 MB simply use +100M.

discover . - sort f -measurement +1G -print

42. What’s the shell script?
A shell script is a set of shell instructions with some programming constructs e.g. if and for loop, which lets you automate some repetitive process. For instance, you possibly can write a shell script to the each day cleanup of logs information,  for backing up knowledge for historic use and for different housekeeping jobs, releases, and monitoring.

That is all on this listing of programming questions for telephone interviews. You might need seen that there are solely 42 questions however the title talked about about 50 questions, the place are the remaining 8 questions? Nicely As an alternative of sharing 8 questions I’m sharing with you guys 8 extra articles the place you’ll find the remaining programming questions.  right here you go:

Thanks for studying this far, If you happen to like this text and located it helpful in your telephonic interviews, please share it with your folks and faculties.  Any suggestions to enhance the standard of interview questions shall be extremely appreciated.



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