HackerEarth Software Engineer Interview Questions and Answers

Normal apptitude queations were asked in this round

Q1. Questions on javascript Basic of HTML, CSS
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Q1. What is a pointer to pointer
Ans. 
A pointer to pointer is a variable that stores the memory address of another pointer variable.
• It is used to create dynamic data structures like linked lists and trees.

• It allows multiple levels of indirection.

• It is denoted by ** in C and C++.

• Example: int **ptr;

• Example: ptr = &p; where p is a pointer variable.
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Q2. Class, object, inheritance, polymorphism,dbms
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Q1. What are the main principles of the Java
Ans. 
Main principles of Java include object-oriented programming, platform independence, and automatic memory management.
• Object-oriented programming: Java is based on classes and objects, allowing for encapsulation, inheritance, and polymorphism.

• Platform independence: Java code can run on any platform that has a Java Virtual Machine (JVM) installed.

• Automatic memory management: Java uses garbage collection to automatically m
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Q2. What is the different between == and equals method
Ans. 
The == operator compares the memory addresses of two objects, while the equals method compares the content of two objects.
• The == operator is used to compare the memory addresses of two objects in Java.

• The equals method is used to compare the content of two objects in Java.

• Example: String str1 = new String("hello"); String str2 = new String("hello"); str1 == str2 will return false, but str1.equals(str2) will return true
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Q1. What is jdk, string related questions, basic java oops questions?
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Q1. Question on anagram whether we can form with given strings
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Q2. Play random song from list without repetition
Ans. 
Use Fisher-Yates shuffle algorithm to play songs randomly without repetition.
• Create an array of songs

• Use Fisher-Yates shuffle algorithm to shuffle the array

• Play the first song in the shuffled array

• Remove the first song from the array

• Repeat steps 3-4 until all songs have been played
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Q3. Reverse the linked list
Ans. 
Reverse a linked list
• Iterate through the linked list and change the direction of the pointers

• Keep track of the previous, current, and next nodes

• Set the head of the linked list to the last node after reversing
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Q4. Range sum with the queries
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Q5. Hashing on 2d matrix counting max 1
Ans. 
Hashing algorithm to count maximum number of 1s in a 2D matrix.
• Create a hash table to store the count of 1s in each row.

• Traverse through each row and update the count in the hash table.

• Find the row with the maximum count of 1s in the hash table.

• Return the count of 1s in that row.
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Q6. React interviews hooks
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Equation, ratio and proportion

Q1. What are oops concepts in java, explain real time scenario
Ans. 
OOPs concepts in Java include inheritance, polymorphism, encapsulation, and abstraction.
• Inheritance allows a subclass to inherit properties and methods from a superclass.

• Polymorphism allows objects to take on multiple forms and behave differently based on their context.

• Encapsulation hides the implementation details of an object and only exposes necessary information.

• Abstraction allows for the creation of abstract class...read more
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Q2. Uses of interface, inheritance
Ans. 
Interfaces define contracts for behavior, while inheritance allows for code reuse and polymorphism.
• Interfaces allow for loose coupling and abstraction, enabling multiple implementations of the same behavior.

• Inheritance allows for code reuse and extension of existing classes, reducing code duplication.

• Polymorphism allows objects of different classes to be treated as if they were of the same class, simplifying code and i
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Q3. SQL query for join of tables
Ans. 
SQL query for joining tables
• Use JOIN keyword to combine two or more tables based on a related column

• Specify the columns to be selected using SELECT keyword

• Use ON keyword to specify the condition for joining the tables

• Different types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN
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Q4. Java concepts used in your project
Ans. 
Used Java concepts such as inheritance, polymorphism, and exception handling in my project.
• Implemented inheritance to create a base class and derived classes with specific functionalities.

• Utilized polymorphism to allow objects of different classes to be treated as if they were of the same class.

• Implemented exception handling to handle errors and prevent program crashes.

• Used interfaces to define a set of methods that a ...read more
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Q5. Overloading vs overriding, practical uses
Ans. 
Overloading is having multiple methods with the same name but different parameters. Overriding is having a method in a subclass with the same name and parameters as a method in the superclass.
• Overloading is used to provide different ways to call a method with different parameters

• Overriding is used to provide a specific implementation of a method in a subclass

• Overloading is resolved at compile-time while overriding is r...read more
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