Full Information on String Interview Preparation

What’s String?

Strings are thought-about a information sort usually and are sometimes represented as arrays of bytes (or phrases) that retailer a sequence of characters. Strings are outlined as an array of characters. The distinction between a personality array and a string is the string is terminated with a particular character ‘’

Complete Guide to String interview preparation

Full Information to String interview preparation

Under are some examples of strings:

“geeks” , “for”, “geeks”, “GeeksforGeeks”, “Geeks for Geeks”, “123Geeks”, “@123 Geeks”

How String is represented in Reminiscence?

In C, a string may be referred to both utilizing a personality pointer or as a personality array. When strings are declared as character arrays, they’re saved like different kinds of arrays in C. For instance, if str[] is an auto variable then the string is saved within the stack section, if it’s a worldwide or static variable then saved within the information section, and so on.

Representation of String

Illustration of String

The way to Declare Strings in varied languages?

Under is the illustration of strings in varied languages:


#embody <stdio.h>


int foremost()



    char str[] = "Geeks";



    printf("%s", str);


    return 0;




#embody <iostream>

#embody <string>

utilizing namespace std;


int foremost()




    string str1 = "Welcome to GeeksforGeeks!";



    string str2("A Pc Science Portal");



    cout << str1 << endl << str2;


    return 0;



import java.io.*;

import java.lang.*;


class Take a look at {

    public static void foremost(String[] args)



        String s = "GeeksforGeeks";



        System.out.println("String s = " + s);



        String s1 = new String("GeeksforGeeks");



        System.out.println("String s1 = " + s1);





String1 = 'Welcome to the Geeks World'

print("String with the usage of Single Quotes: ")



String1 = "I am a Geek"

print("nString with the usage of Double Quotes: ")



String1 =

print("nString with the usage of Triple Quotes: ")



String1 =



print("nCreating a multiline String: ")






$web site = 'Welcome to GeeksforGeeks';


echo $web site;




<!DOCTYPE html>





        JavaScript Strings








    <h2>JavaScript Strings</h2>


    <p id="GFG"></p>



    <!-- Script to retailer string in variable -->




        var x = "Welcome to GeeksforGeeks!";

        doc.getElementById("GFG").innerHTML = x;





Basic Operations carried out on String:

Right here we’re offering you with some must-know ideas of string:

1. Concatenation of Strings

The method of mixing a couple of string collectively is named Concatenation. String Concatenation is the approach of mixing two strings. 

Concatenation of Strings

Concatenation of Strings

There are two methods to concatenate two strings:

a) String concatenation with out utilizing any inbuilt strategies:

Under is the algorithm for the Concatenation of two strings:


3. SET I = 0.
4. Repeat Steps 5 and 6 whereas I < LEN1-1:
5.     STR3[I] = STR1[I].
6.     SET I = I+1.
7. SET J = 0.
8. Repeat Steps 9 to 11 whereas I < (LEN1 + LEN2 - 2):
9.     STR3[I] = STR2[J].
10.    J = J+1.
11.    I = I+1.

b) String concatenation utilizing inbuilt strategies:

2. Discover in String

A really primary operation carried out on Strings is to search out one thing within the given complete string. Now, this may be to discover a given character in a string, or to discover a full string in one other string.

Find in String

Discover in String

a) Discover a character in string:

Given a string and a personality, your process is to search out the primary place of the character within the string. Some of these issues are very aggressive programming the place you must find the place of the character in a string.

b) Discover a substring in one other string:

Think about there to be a string of size N and a substring of size M. Then run a nested loop, the place the outer loop runs from 0 to (N-M) and the interior loop from 0 to M. For each index test if the sub-string traversed by the interior loop is the given sub-string or not. 

An environment friendly resolution is to make use of a O(n) looking out algorithm like KMP algorithm, Z algorithm, and so on.

Language implementations: 

3. Substitute in String

Many instances, it is rather vital to make corrections in strings. Changing a personality, phrase or phrase in a String is one other quite common operation carried out on Strings.

The best strategy to resolve the given drawback is to traverse the string S and when any string S1 is discovered as a substring within the string S then substitute it by S2. Comply with the steps beneath to resolve this drawback:

  • Initialize a string ans to retailer the resultant string after changing all of the occurrences of the substring S1 to S2 within the string S.
  • Iterate over the characters of the string S utilizing variable i and carry out the next steps:
    • If the prefix substring of the string S is the same as S1 from the index i, then add the string S2 within the string ans.
    • In any other case, add the present character to the string ans.
  • After finishing the above steps, print the string ans because the end result.

4. Discovering the Size of String

Probably the most common operations on String is to search out the size/measurement of a given string. Size is outlined because the variety of characters in a string is known as the size of that string.

Finding the Length of String

Discovering the Size of String

There are two methods to concatenate two strings:

a) Size of string with out utilizing any inbuilt strategies: 

Under is the algorithm for locating the size of two strings:

1. SET LEN = 0 AND I = 0.
2. Repeat Steps 3 to 4 whereas STRING[I] will not be NULL:
3. LEN = LEN + 1.
4. SET I = I + 1.
5. Exit.

b) Size of string utilizing inbuilt strategies:

5. Trim a String

Areas or particular characters are quite common in Strings. So it is very important know methods to trim such characters in String.

Under is a Easy Answer 

1) Iterate by all characters of given string, do following
   a) If present character is an area, then transfer all subsequent characters one place again and reduce size of the end result string.

The time complexity of the above resolution is O(n2).

A Higher Answer can resolve it in O(n) time. The concept is to maintain observe of rely of non-space character seen to this point. 

1) Initialize ‘rely’ = 0 (Depend of non-space character seen to this point)
2) Iterate by all characters of given string, do following
     a) If present character is non-space, then put this character at index ‘rely’ and increment ‘rely’
3) Lastly, put ‘’ at index ‘rely’

6. Reverse and Rotation of a String

Reverse operation is interchanging the place of characters of a string such that the primary turns into the final, the second turns into the second final, and so forth.

a) Rotations of a String:

Rotation of a String

Rotation of a String

Think about a string “geeks”, now all attainable rotations for this will probably be:

  • geeks
  • eeksg
  • eksge
  • ksgee
  • sgeek

b) Reverse a String:

The reversing of a string is nothing however merely substituting the final component of a string to the first place of the string.

Reverse a String

A subsequence is a sequence that may be derived from one other sequence by eradicating zero or extra components, with out altering the order of the remaining components.

Extra usually, we will say that for a sequence of measurement n, we will have (2n-1) non-empty sub-sequences in whole.

For instance, Think about the string “geeks”, there are 15 sub-sequences. 

g, e, e, ok, s,
ge, ge, gk, gs, ee, ek, es, ek, es, ks,
gee, gek, ges, gek, ges, gks, eek, ees, eks, eks,
geek, gees, eeks,


A substring is a contiguous a part of a string, i.e., a string inside one other string.

Normally, for a string of measurement n, there are n*(n+1)/2 non-empty substrings.

For instance, Think about the string “geeks”, There are 15 non-empty substrings.
The subarrays are:

g, ge, gee, geek, geeks,
e, ee, eek, eeks,
e, ek, eks,
ok, ks, 


A Binary String is a particular sort of string made up of solely two kinds of characters, resembling 0 and 1.
For Instance:  

Enter: str = "01010101010"
Output: Sure, it's a Binary String

Enter: str = "geeks101"
Output: No, it's not a Binary String

A string is alleged to be a palindrome if the reverse of the string is similar because the string. 
For instance,

“abba” is a palindrome, however “abbc” will not be a palindrome.

Palindrome String

Lexicographical sample is the sample based mostly on the ASCII worth or may be mentioned in dictionary order. We contemplate the lexicographic order of characters as their order of ASCII worth. Therefore the lexicographical order of characters will probably be 

‘A’, ‘B’, ‘C’, …, ‘Y’, ‘Z’, ‘a’, ‘b’, ‘c’, …, ‘y’, ‘z’.

Sample looking out is looking out a given sample within the string. It’s a sophisticated matter of string. The Sample Looking out algorithms are generally additionally known as String Looking out Algorithms and are thought-about as part of the String algorithms. These algorithms are helpful within the case of looking out a string inside one other string.

Pattern Searching

Sample Looking out

High Ttheoretical Interview Questions

S.no Query Reply
1 What are other ways to create String Object? View
2 Can we evaluate String utilizing the == operator? What’s the danger? View
3 The way to substitute a substring with ( from a string ? View
4 What’s the distinction between String and StringBuffer in java? View
5 How do I convert a string model of a quantity in an arbitrary base to an integer? View
6 How do you evaluate two Strings in Java? View
7 What’s String in Knowledge Constructions?   View
8 What’s the distinction between Strings vs. Char arrays?   View
9 What’s a null-terminated String?   View
10  Reverse a String utilizing Stack View
11 Distinction between String, StringBuffer and StringBuilder? View
12 Why String is immutable or last in Java View
13 What Is the String Fixed Pool? View
14 Take away Invalid Parentheses View
15 What’s the usage of the substring() methodology? View
16 Expian how can I take away the trailing areas from a String View
17 Clarify how can I pad a string to recognized size View
18 Clarify how will you inform whether or not two string are the identical View
19 The way to test if the String is empty? View
20 Can we use a string within the change case in java? View
21 How string concatenation utilizing the + operator works in Java? View
22 What are the completely different string strategies in Java? View
23 What do you imply by StringJoiner? View
24 The way to convert string illustration of checklist to a listing? View
26 How do I tokenize a string in C++? View
27 Print all permutations of the String ? View
28 How do you reverse a given string in place?  View
29 The way to convert a byte array to String? View
30 The way to calculate whole variety of vowels in String? View
31 Write a program to transform a string in lowercase View
32 Write a program to transform a string in uppercase. View
33 Write a C++ program to search out the size of the string. View
34 In what manner ought to two whether or not they’re anagrams?strings be in comparison with decide  View
35 Write a java program to tOGGLE every phrase in string? View
36 The way to convert String to Date in java? View
37 Java Program to reverse a given String with preserving the place of area View
38 Multiply Massive Numbers represented as Strings View
39 String “indexOf” Methodology View

High 50 interview coding query

Straightforward Issues on String


Medium Issues on String


Laborious Issues on String

Benefits of utilizing String:

  • Strings present us very useful string algorithms for fixing very complicated issues with much less time complexity.
  • String offers us a string library to create string objects which can enable strings to be dynamically allotted and in addition boundary points are dealt with inside class library.
  • String helps as a base for a lot of information buildings resembling tries, suffix timber, suffix arrays, ternary search timber, and far more.
  • String offers us varied inbuilt capabilities underneath string library resembling type(), substr(i, j), evaluate(), push_back() and plenty of extra.
  • In C language strings can have compile-time allocation and dedication of measurement. This makes them extra environment friendly, sooner run-time on the time of utilizing them.
  • In C++ we don’t must predefine the dimensions of a string.

Disadvantages of String:

  • Strings are usually sluggish in performing operations like enter, output.
  • In JAVA strings are  immutable they can’t be modified or modified
  • In JAVA you can’t prolong string class which implies overriding strategies in string class will not be attainable.
  • C strings are mounted in measurement and are usually not dynamic.

Utility of String:

  • Info Retrieval: String functions assist us to retrieve info from unknown information sources( giant datasets used as enter) together with the assistance of string matching/retrieval module helps us to retrieve vital info.
  • Encoding/Decoding(Cipher Textual content Era): Strings can be utilized for encoding and decoding for the protected switch of information from sender to receiver to ensure nobody in the best way of transmission will get to learn your information as they might carry out each lively and passive assaults. The textual content you switch as a message will get ciphered on the sender’s finish and decoded on the receiver’s finish.
  • Plagiarism Checker: Strings can be utilized to search out Plagiarism in codes, and contents in a little or no period of time utilizing string matching algorithms. Utilizing this the pc might simply inform us the proportion of code, and textual content written by any two customers matches by how a lot p.c.
  • Improved Filters For The Approximate Suffix-Prefix Overlap Downside: Strings and its algorithms functions assist us to supply improved Filters for the Approximate Suffix-Prefix Overlap Downside. The approximate suffix-prefix overlap drawback is to search out all pairs of strings from a given set such {that a} prefix of 1 string is just like a suffix of the opposite.

Actual-Time Utility of String:

  • Search Engines: Strings can be utilized in lots of search engine strategies. A lot of the information can be found on the web within the type of textual information. As a consequence of enormous quantity of uncategorized textual content information, it turns into actually tough to look a specific content material. Internet serps arrange the info and categorize the info string matching algorithms.
  • Intrusion Detection System: Strings can be utilized in intrusion detection techniques. Packets that comprise intrusion-related key phrases are discovered by making use of string matching algorithms.
  • Bioinformatics: Strings can be utilized within the area of Bioinformatics( DNA sequencing). String matching module can be utilized to resolve points or issues concerning genetic sequences and to search out the patterns in DNA.
  • Spam Detection: Strings can be utilized to function a spam detection system because the idea of string matching algorithm will probably be utilized right here. Spam (undesirable emails) might trigger nice monetary loss. All of the spam filters use the idea of string matching to establish and discard the spam.

Steadily requested questions (FAQs) on String

1. Is string a linear information construction?

Sure, string is a linear information construction.

2. The place are strings used?

It’s used to retailer the sequence of characters.

3. Is string a knowledge sort?

A string is usually thought-about a knowledge sort and is commonly carried out as an array information construction of bytes (or phrases) that shops a sequence of components, sometimes characters, utilizing some character encoding.

4. Why is textual content referred to as string?

Textual content are additionally referred to as string as a result of it consists of sequence of characters like string.

5. What are characters in a string?

Every digit in a string is a personality and character is a single visible object used to characterize textual content, numbers, or symbols.


After the dialogue, we concluded that Strings are a easy methodology to retailer some textual info and Strings are an array of characters that terminate with a null character ‘’. The distinction between a personality array and a string is that, not like the character array, the string ends with a null character. Other than this now we have additionally mentioned High theoretical interview questions in addition to High 50 interview coding query on string which can enable you to to deal with interview issues.

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