Top Twenty String Algorithm Questions From Coding Interviews

In this article, nosotros are going to run into top xx String based coding interview interrogation together with their solution to assist programmers improve ready for interviews. The string is 1 of the most of import information construction together with available inwards almost every programming linguistic communication similar Java, C, C++, Python, Perl, together with Ruby. Though in that location implement differ the essence remains same similar String is NULL terminated graphic symbol array inwards C but String is an object inwards Java, over again backed past times graphic symbol array. The string is likewise available on weekly typed languages similar Python together with Perl.  This is why y'all volition e'er let on some String based coding interrogation on programming interview.

Even inwards your college days, y'all would direct hold solved lots of coding problems based upon String similar reversing String inwards place, checking if String is a palindrome, checking if 2 strings are an anagram of each other, calculating permutations of String etc.

The coding questions from programming interviews are likewise non rattling dissimilar from that, exactly yeah it gets slightly to a greater extent than hard amongst your experience.

For example, inwards your get-go few programming chore interviews, y'all may let on questions similar removing duplicates from String or replacing all spaces with %20, exactly every bit y'all acquire to a greater extent than experience together with apply for senior developer position, y'all tin hold off tough questions about how to let on the longest palindrome inwards a string or printing all permutations of String etc.

This article contains both tardily together with hard String coding questions for your preparation. I direct hold non posted the solution right behind the work therefore that y'all tin give it a shot earlier checking the solution. You tin solve these String based coding interrogation on whatever linguistic communication of your alternative similar C, C++, Java, Python or fifty-fifty JavaScript.

Btw, if y'all are novel to Data Structure together with Algorithms or desire to revise key algorithms earlier interviews, I propose y'all bring together a comprehensive course of pedagogy like Data Structures together with Algorithms: Deep Dive Using Java on Udemy. It's 1 of the best course of pedagogy together with covers both basic algorithms together with information construction similar the array, linked list, binary tree exactly likewise advanced concepts similar bucket sort, counting sort together with other O(n) sorting algorithms.

20 String Algorithm based Coding Interview Questions

Here is my collection of some of the most oft asked String based coding questions from programming interview. Remember, in that location are many algorithms to solve the same problem, together with y'all should know that, mainly to handgrip the follow-up interrogation better.

Also recall to solve the same interrogation using both recursion together with iteration, every bit interviewer actually similar to inquire iterative version if y'all come upwards up amongst a recursive algorithm together with vice-versa.

Nevertheless, if y'all run into your favorite interrogation is non included inwards the list, experience costless to suggest, I volition include it.

You tin likewise postal service interrogation asked to y'all on your interview together with y'all direct hold non constitute its solution yet. Some questions are however unsolved or solution is non yet posted on my blog. Also, the difficulty degree increases every bit y'all motility questions.

1) How to Print duplicate characters from String? (solution)

To start with, nosotros direct hold a uncomplicated String related coding interrogation oft asked inwards programming interviews. You demand to write a plan in Java, C, C++, Python, Perl, or Ruby to impress duplicate characters from a given String.

For example, if String is "Java" together with therefore the plan should impress "a". Bonus points if your plan is robust together with handles dissimilar kinds of input e.g. String without duplicate, nil or empty String etc. Bonus points if y'all likewise write unit of measurement tests for normal together with border cases.

2) How to cheque if 2 Strings are anagrams of each other? (solution)

H5N1 uncomplicated coding work based upon String, exactly could likewise live on asked amongst numbers. You demand to write a Java plan to cheque if 2 given strings are anagrams of Each other. Two strings are anagrams if they are written using the same exact letters, ignoring space, punctuation, together with capitalization. Each missive of the alphabet should direct hold the same count inwards both strings. For example, the Army and Mary are an anagram of each other.

3) How to plan to impress get-go non repeated graphic symbol from String? (solution)

One of the most mutual string interview questions: Find the get-go non-repeated (unique) graphic symbol inwards a given string. for Example, if given String is "Morning" then it should impress "M". This interrogation demonstrates the efficient utilization of the hash tabular array information structure.

We scan the string from left to right counting the pose out occurrences of each graphic symbol inwards a Hashtable. Then nosotros perform a instant overstep together with cheque the counts of every character. Whenever nosotros hitting a count of 1 nosotros render that character, that’s the get-go unique letter. Be prepared for follow-up interrogation for improving retentiveness efficiency, solving it without the hash tabular array every bit well.

Btw, if y'all are non familiar amongst hash tabular array together with other essential information construction together with therefore y'all should get-go acquire through a beginners algorithms course of pedagogy like solution) Your undertaking is to write a plan to contrary String inwards Java without using StringBuffer class. You likewise demand to render both iterative together with recursive algorithm for String reversal. You tin utilization other String utility methods e.g. charAt(), toCharArray() or substring() from java.lang.String class.

5) How to cheque if a String contains exclusively digits?  (solution)

You demand to write a plan to cheque a String contains exclusively numbers past times using Regular human face inwards Java. You tin utilization Java API exactly a solution without using Java API volition live on improve because that is what interviewer tin e'er ask.

6) How to let on duplicate characters inwards a String? (solution)

You demand to write a plan to impress all duplicate graphic symbol together with their count inwards Java. For example, if given String is "Programming" together with therefore your plan should print
g : 2
r : 2
one thousand : 2

7) How to count a pose out of vowels together with consonants inwards a String? (solution)

One of easiest String interrogation y'all volition ever see. You direct hold to write a Java plan which volition convey a String input together with impress out a pose out of vowels together with consonants on that String. For example, if the input is "Java" together with therefore your plan should print "2 vowels together with 2 consonants".

If y'all acquire this interrogation on Interview, y'all should clarify whether String tin comprise numbers, exceptional characters or non similar anything other than vowels together with consonants.

This is an of import tip for doing good on interviews. I likewise propose revising essential information construction earlier interviews past times joining Data Structures inwards Java: An Interview Refresher course on Educative.

8) How to count the occurrence of a given graphic symbol inwards String? (solution)

If the interviewer asks y'all to count the occurrence of to a greater extent than than 1 graphic symbol than y'all tin either utilization an array, hash tabular array or whatever additional information structure. In club to solve this problem, y'all are non allowed to do so. Your method must render a count of a given character, for example, if input String is "Java" together with given graphic symbol is 'a' together with therefore it should render 2. Bonus betoken if y'all handgrip case, nil together with empty String together with come upwards up amongst unit of measurement tests.

9) How to convert numeric String to an int? (solution)

H5N1 classical coding interview interrogation based upon String. You demand to write a method similar atoi() from C/C++, which takes a numeric String together with render its int equivalent. For example, if y'all overstep "67263" to the plan together with therefore it should render 67263.

Make certain your solution is robust similar it should live on able to handle + together with - character, nil together with empty String, integer overflow together with other corner cases.  Bonus points if y'all come upwards up amongst goodness unit of measurement seek cases.

By the way, if your interviewer doesn't advert to y'all about atoi() then y'all tin likewise utilization Java API's parseInt() or valueOf() method to solve this problem.

10) How to supervene upon each given graphic symbol to other e.g. blank amongst %20? (solution)

Write a Java plan to supervene upon a given graphic symbol inwards a String to other provided character, for example, if y'all are asked to supervene upon each blank inwards a String with %20, similar to URL encoding done past times the browser therefore that Server tin read all asking parameters. For example, if the input is "Java is Great" together with asked to supervene upon infinite amongst %20 together with therefore it should live on "Java%20is%20Great".

11) How to let on all permutations of String? (solution)

I direct hold seen this String interview interrogation on many interviews. It has an tardily recursive solution exactly things acquire actually tricky when Interviewer asks y'all to solve this interrogation without using recursion. You tin utilization a Stack though. Write a plan to impress all permutations of a String inwards Java, for example, the if input is "xyz" then it should print "xyz", "yzx", "zxy", "xzy", "yxz", "zyx".

12) How to contrary words inwards a judgement without using a library method? (solution)

Write a function, which takes a String discussion together with returns judgement on which words are reversed inwards club similar if the input is "Java is best programming language", the output should live on "language programming best is Java".

13) How to cheque if String is Palindrome? (solution)

Another tardily coding interrogation based upon String, I am certain y'all must direct hold done this numerous time. Your plan should render truthful if String is a Palindrome, otherwise false. For example, if the input is "radar", the output should live on true, if the input is "madam" output volition live on true, together with if the input is "Java" output should live on false.

14) How to take duplicate characters from String? (solution)

This is 1 of the interesting String question, which likewise has lots of variants. You demand to take duplicate characters from a given string keeping exclusively the get-go occurrences. For example, if the input is ‘bananas’ the output volition live on ‘bans’. Pay attending to what output could be, because if y'all seem closely master copy club of characters are retained the inwards output.

This is where many developers brand the mistake of shorting graphic symbol array of String together with removing duplicates, similar to how y'all take duplicates from an array. That destroys the master copy club of characters together with volition non live on the right solution inwards this case.

15) How to cheque if a String is a valid shuffle of 2 String? (solution)

One to a greater extent than hard String algorithm based coding interrogation for senior developers. You are given iii strings: first,  second, together with third.  Third String is said to live on a shuffle of get-go together with instant if it tin live on formed past times interleaving the characters of get-go together with instant String inwards a agency that maintains the left to right ordering of the characters from each string.

For example, given get-go = "abc" and instant = "def",  third = "dabecf"  is a valid shuffle since it preserves the graphic symbol ordering of the 2 strings. So, given these iii strings write a business office that detects whether the 3rd String is a valid shuffle of get-go together with instant String.

16) Write a plan to cheque if a String contains some other String similar indexOf ()? (solution)

You demand to write a business office to search for the beingness of a string (target) inwards some other string (source). The business office takes 2 strings every bit the input together with returns the index where the instant string is found. If the target string cannot live on found, together with therefore render -1.

If y'all are a Java developer, together with therefore y'all tin relate its behaviour to indexOf() method from java.lang.String class. This interrogation is likewise asked every bit Code together with algorithm to cheque if a given brusque string is a substring of the primary string. Can y'all acquire a linear solution (O(n)) if possible?

17) How to render highest occurred graphic symbol inwards a String? (solution)

You demand to write a business office to implement an algorithm which volition direct hold a string of characters together with should let on the highest occurrence of the graphic symbol together with display it. For illustration if input is "aaaaaaaaaaaaaaaaabbbbcddddeeeeee" it should render "a".

18) Write a plan to take a given graphic symbol from String? (solution)

One of my favorite coding question, when I interview Java developers. You demand to write a Java method which volition direct hold a String together with a graphic symbol to live on removed together with render a String, which doesn't has that graphic symbol e.g remove(String word, char ch).

You demand to render both iterative together with recursive solution of this method together with likewise has to write JUnit tests to comprehend cases similar nil together with empty String, input which exclusively contains a missive of the alphabet to live on removed, String which doesn't comprise given graphic symbol etc.

For to a greater extent than coding together with algorithmic questions, y'all tin likewise cheque the Cracking the Coding Interview sixth Edition book, which contains over 189 Programming Questions together with Solutions.

19) Write a plan to let on the longest palindrome inwards a string? (solution)

This is 1 of the tough coding interrogation based upon String. It's hard to intend nigh an algorithm to solve this work until y'all direct hold practiced well. What makes it to a greater extent than hard is the constraint that your solution has O(n) fourth dimension complexity together with O(1) infinite complexity.

20) How to sort String on their length inwards Java? (solution)

Write a Program to sort String on their length inwards Java? Your method should direct hold an array of String together with render a sorted array based upon the length of String. Don't forget to write unit of measurement tests for your solution.


That's all on this listing of 15 String Algorithm based coding questions. These are a actually goodness interrogation to ready for programming chore interviews, non exclusively y'all tin hold off the same interrogation on a existent interview exactly likewise it volition ready y'all how to tackle algorithmic coding interview questions. Even if y'all don't let on the same question, y'all would live on able to apply the cognition y'all gain past times solving these interrogation past times yourself.

Always remember, y'all are judged past times the code y'all write, therefore e'er write production character code, which would overstep the full general test, corner cases, invalid inputs, robustness seek together with likewise overstep the functioning test.  Whenever asked to solve a coding problem, e'er intend nigh all possible input together with write a seek for that.


Further Learning
Data Structures together with Algorithms: Deep Dive Using Java
see here)

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133 nitty-gritty Java interview questions of the final v years (see here)

Top thirty linked listing coding interview questions (see here)

Top 50 Java Programs from Coding Interviews (see here)

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100+ Data Structure Coding Problems from Interviews (questions)

10 Free Data Structure together with Algorithm Courses for Programmers (courses)

How to convert a linked listing to an array inwards Java? (example)

How to let on a missing value from an array containing 1 to 100? (solution)

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My favorite costless courses to acquire information Structure inwards depth (FreeCodeCamp)

Top v Books to Learn Data Structure together with Algorithms (books)

How to count the pose out of leafage nodes inwards a given binary tree inwards Java? (solution)

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50+ Data Structure together with Algorithms Problems from Interviews (questions)

Iterative PreOrder traversal inwards a binary tree (solution)

Recursive InOrder traversal Algorithm (solution)

10 Algorithms Courses to Crack Programming Job Interviews (courses)

Thanks for reading this article therefore far. If y'all similar these questions together with therefore delight portion amongst your friends together with colleagues. If y'all direct hold whatever other interesting interrogation which y'all direct hold faced on interviews, drib us a note.

P. S. - If y'all are looking for some Free Algorithms courses to improve your agreement of Data Structure together with Algorithms, together with therefore y'all should likewise cheque the Easy to Advanced Data Structures course of pedagogy on Udemy. It's authored past times a Google Software Engineer together with Algorithm proficient together with its completely costless of cost.

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