60+ Amdocs Interview Questions and Answers

Find the maximum sum of an increasing subsequence of length K in an array.

• Iterate through the array and maintain a dynamic programming table to store the maximum sum of increasing subsequences of different lengths.

• For each element, check all previous elements to find the increasing subsequences and update the maximum sum accordingly.

• Return the maximum sum of the increasing subsequence of length K.

• Example: For input [1, 2, 5, 4, 8] and K = 3, the maximum sum increasing subsequ...read more

Identify the first non-repeating character in a given string and return it, or '#' if none exists.

• Iterate through the string to count the frequency of each character

• Iterate through the string again to find the first character with frequency 1

• Return the first non-repeating character or '#' if none exists

Implement a function to convert a string to an integer, ignoring non-numeric characters and considering negative numbers.

• Iterate through the characters of the string and check if they are numeric.

• Handle negative numbers by checking the first character of the string.

• Ignore non-numeric characters while converting the string to an integer.

• Return 0 if there are no numbers in the string.

• Ensure the resulting number is within the given constraints.

Count the number of subarrays where the number of 0s is equal to the number of 1s in a given array of 0s and 1s.

• Iterate through the array and keep track of the count of 0s and 1s encountered so far.

• Use a hashmap to store the count of 0s and 1s encountered at each index.

• For each index, check if the count of 0s and 1s encountered so far are equal. If yes, increment the total count of subarrays.

Detect if an array contains a Pythagorean triplet by checking if x^2 + y^2 = z^2.

• Iterate through all possible combinations of three numbers in the array.

• Check if the sum of squares of any two numbers is equal to the square of the third number.

• Return 'yes' if a Pythagorean triplet is found, otherwise return 'no'.

Find all paths in a binary tree where the sum of node values equals a given value 'K'.

• Traverse the binary tree using depth-first search (DFS) and keep track of the current path and its sum.

• When reaching a leaf node, check if the sum equals 'K' and add the path to the result.

• Continue DFS traversal for both left and right children, passing updated path and sum.

• Return the list of paths that sum up to 'K'.

The task is to determine if a given integer is a Fibonacci number or not.

• Iterate through the Fibonacci sequence until the current number exceeds the given integer 'N'.

• Check if the given integer 'N' matches any number in the Fibonacci sequence.

• If a match is found, output 'YES'; otherwise, output 'NO'.

Reverse a given stack of integers using recursion without using extra space or loop constructs.

• Use recursion to pop all elements from the original stack and store them in function call stack.

• Once the stack is empty, push the elements back in reverse order using recursion.

• Base case of recursion should be when the original stack is empty.

Implement a priority queue using Heap data structure with functions like push, pop, getMaxElement, and isEmpty.

• Implement push() function to insert element into the priority queue.

• Implement pop() function to delete the largest element from the queue.

• Implement getMaxElement() function to return the largest element.

• Implement isEmpty() function to check if the queue is empty.

Check if a given string is a palindrome after removing special characters, spaces, and converting to lowercase.

• Remove special characters and spaces from the input string

• Convert the string to lowercase

• Check if the modified string is a palindrome by comparing characters from start and end

Calculate the Nth Fibonacci number efficiently using dynamic programming.

• Use dynamic programming to store previously calculated Fibonacci numbers to avoid redundant calculations.

• Start with base cases F(1) and F(2) as 1, then iterate to calculate subsequent Fibonacci numbers.

• Time complexity can be optimized to O(N) using dynamic programming.

• Example: For N = 5, the 5th Fibonacci number is 5.

Print all prime numbers within the range from 2 to N.

• Iterate from 2 to N and check if each number is prime

• A prime number is a number greater than 1 that has no positive divisors other than 1 and itself

• Use a nested loop to check divisibility by numbers less than the current number

Calculate the Nth Fibonacci number using the given formula and constraints.

• Implement a function to calculate the Nth Fibonacci number using the formula F(n) = F(n-1) + F(n-2) with base cases F(1) = F(2) = 1.

• Use dynamic programming or recursion to efficiently compute the Fibonacci number for large N values.

• Ensure the input N is within the constraints 1 <= N <= 10000.

• Example: For N = 5, the output should be 5 as the 5th Fibonacci number is 5.

Write a SQL query to join two tables on a common attribute and select matching records.

• Use the JOIN keyword to combine tables A and B on the common attribute ID

• Specify the common attribute in the ON clause of the JOIN

• Select the desired columns (ID_NAME) from the joined tables

Race horses in groups of 5, then race the winners to determine the top 3 fastest horses.

• Divide the 25 horses into 5 groups of 5 horses each.

• Race the horses in each group to determine the fastest horse in each group.

• Race the winners from each group to determine the top 3 fastest horses.

Convert string to integer without using inbuilt function

• Iterate through each character and multiply by 10 and add the integer value of the character

• Use ASCII values to convert character to integer

• Handle negative numbers separately

Right outer join is a type of join operation that returns all the rows from the right table and the matching rows from the left table.

• Right outer join is denoted by the RIGHT JOIN keyword in SQL.

• It is used to combine rows from two tables based on a related column.

• In the result set, unmatched rows from the right table will have NULL values for the columns of the left table.

• A real-world scenario for using a right outer join is when analyzing customer data and sales data. The ri...read more

To determine which switch controls which bulb with only one entry to the bulb room.

• Turn on the first switch and leave it on for a few minutes, then turn it off.

• Turn on the second switch and enter the room.

• The bulb that is on corresponds to the second switch, the bulb that is off and warm corresponds to the first switch, and the bulb that is off and cold corresponds to the third switch.

Essential UNIX commands include ls, cd, pwd, mkdir, and rm.

• ls - list directory contents

• cd - change directory

• pwd - print working directory

• mkdir - make directory

• rm - remove files or directories

Primary key uniquely identifies a record in a table, while unique key ensures no duplicate values in a column.

• Primary key is used to uniquely identify each record in a table

• Primary key does not allow NULL values

• Unique key ensures that all values in a column are unique

• Unique key allows NULL values, except for the column with unique constraint

• A table can have only one primary key, but multiple unique keys

Left Outer Join includes all records from the left table and matching records from the right table. Right Outer Join includes all records from the right table and matching records from the left table.

• Left Outer Join returns all records from the left table and the matched records from the right table. Unmatched records from the right table will have NULL values.

• Right Outer Join returns all records from the right table and the matched records from the left table. Unmatched reco...read more

To find the second highest salary in a table, you can use a SQL query with the ORDER BY and LIMIT clauses.

• Use a SQL query to select the distinct salaries in descending order: SELECT DISTINCT salary FROM table_name ORDER BY salary DESC

• Use the LIMIT clause to retrieve the second row: LIMIT 1,1

• Combine both queries to find the second highest salary: SELECT DISTINCT salary FROM table_name ORDER BY salary DESC LIMIT 1,1

Run time polymorphism in C++ allows objects of different classes to be treated as objects of a common parent class.

• Run time polymorphism is achieved through virtual functions and function overriding.

• It allows a function to behave differently based on the object it is called on.

• Example: Using a base class pointer to call a virtual function that is overridden in a derived class.

Use the 3-liter and 5-liter cans to measure exactly 4 liters of water.

• Fill the 3-liter can and pour it into the 5-liter can, leaving 2 liters in the 3-liter can.

• Empty the 5-liter can, then pour the 2 liters from the 3-liter can into the 5-liter can.

• Fill the 3-liter can again and pour it into the 5-liter can, which already has 2 liters, making it 4 liters.

Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity. Denormalization is the opposite process, adding redundancy to improve read performance.

• Normalization involves breaking down a table into smaller tables and defining relationships between them to reduce redundancy.

• Denormalization involves combining tables to reduce the number of joins needed for queries, improving read performance.

• Normalization helps maintain data int...read more

Recursion is a process in which a function calls itself repeatedly until a base condition is met.

• Recursion involves breaking down a problem into smaller subproblems and solving them recursively.

• It uses a stack to keep track of function calls and their parameters.

• Examples include factorial, Fibonacci sequence, and binary search.

• Compiler executes recursion by allocating memory for each function call and storing the return address and local variables on the stack.

• It then pops th...read more

Singleton class in Java ensures that a class has only one instance and provides a global point of access to it.

• Singleton class is implemented by making the constructor private to prevent instantiation from outside the class.

• It provides a static method to access the single instance of the class.

• The instance is created only once and reused throughout the application.

• Example: Logger class in Java can be implemented as a Singleton to ensure only one instance is used for logging.

A friend function in C++ is a function that is not a member of a class but has access to the private and protected members of the class.

• Friend functions are declared inside a class with the keyword 'friend'.

• They can access private and protected members of the class they are friends with.

• Friend functions are not member functions of the class.

• Example: friend void displayDetails(Student);

Python is a high-level programming language known for its simplicity and readability. Constructors are special methods used to initialize objects in classes.

• Python is a versatile programming language used for web development, data analysis, artificial intelligence, and more.

• Constructors in Python are special methods with the __init__() function that initialize objects when they are created.

• Arrays in Python are data structures that can hold multiple values of the same type. Th...read more

Swapping two character variables without using third

• Use XOR operator to swap two variables without using third variable

• Assign the XOR of both variables to the first variable

• Assign the XOR of the first variable and second variable to the second variable

A program demonstrating recursion using factorial function.

• Recursion is a technique where a function calls itself.

• Factorial function is a classic example of recursion.

• Each recursive call creates a new stack frame.

• The base case is when the input is 1, and the function returns 1.

• The final result is the product of all the recursive calls.

• Example: factorial(5) = 5 * factorial(4) = 5 * 4 * factorial(3) = ... = 5 * 4 * 3 * 2 * 1 = 120.

Garbage collector in Java is a built-in mechanism that automatically manages memory by reclaiming unused objects.

• Garbage collector runs in the background to identify and remove objects that are no longer needed.

• It helps prevent memory leaks and optimize memory usage.

• Examples of garbage collectors in Java include Serial, Parallel, CMS, and G1.

The data structure used in recursion is a stack.

• Recursion uses a stack data structure to keep track of function calls.

• Each time a function is called, its parameters and local variables are pushed onto the stack.

• When the function returns, the values are popped off the stack.

• This allows the program to keep track of where it is in the recursive process.

• Examples of recursive algorithms that use a stack include depth-first search and quicksort.

Primary key uniquely identifies a record in a table, while Unique key ensures uniqueness of a column.

• Primary key can't have null values, Unique key can have one null value

• A table can have only one Primary key, but multiple Unique keys

• Primary key is automatically indexed, Unique key is not necessarily indexed

A static variable in C is a variable that retains its value between function calls.

• Declared using the 'static' keyword

• Retains its value throughout the program's execution

• Useful for maintaining state across function calls

Program to check if a string is a palindrome or not.

• Remove all spaces and convert to lowercase for case-insensitive comparison.

• Compare the first and last characters, then move towards the center until all characters have been compared.

• If all characters match, the string is a palindrome.

• If any characters do not match, the string is not a palindrome.

A friend function is a non-member function that has access to the private and protected members of a class.

• Declared inside the class but defined outside the class scope

• Can access private and protected members of the class

• Not a member of the class but has access to its private members

• Used to allow external functions to access and modify private data of a class

• Can be declared as a friend in another class

Garbage collection in Java is an automatic memory management process.

• It frees up memory by removing objects that are no longer in use.

• It is performed by the JVM in the background.

• It helps prevent memory leaks and improves performance.

• There are different types of garbage collectors in Java, such as Serial, Parallel, CMS, and G1.

• Example: int[] arr = new int[1000]; arr = null; // Garbage collector will remove the array from memory

Addition and Deletion of a node in binary tree

• For addition, traverse the tree to find the appropriate position and add the new node as a leaf

• For deletion, find the node to be deleted and replace it with its successor or predecessor

• In case of deletion, if the node has two children, find the inorder successor and replace it with the node to be deleted

atoi function converts a string to an integer in C.

• The function takes a string as input and returns an integer.

• Leading white spaces are ignored.

• If the string contains non-numeric characters, the function stops conversion and returns the converted value.

• The function returns 0 if the input string is not a valid integer.

• Example: atoi('123') returns 123.

A program to print star pattern

• Use nested loops to print the pattern

• The outer loop controls the number of rows

• The inner loop controls the number of stars to be printed in each row

• Use print() or println() function to print the stars

Refrential integrity ensures that relationships between tables in a database remain consistent.

• It is a database concept that ensures that foreign key values in one table match the primary key values in another table.

• It prevents orphaned records in a database.

• It maintains data consistency and accuracy.

• For example, if a customer record is deleted, all related orders for that customer should also be deleted.

• It is enforced through constraints such as foreign key constraints.

Singleton pattern is a design pattern that restricts the instantiation of a class to one object.

• Used when only one instance of a class is needed throughout the application

• Provides a global point of access to the instance

• Implemented using a private constructor and a static method to return the instance

• Example: Database connection, Logger, Configuration settings

Data structures are used to organize and store data in a computer program.

• Arrays - used to store a collection of elements of the same data type

• Linked Lists - used to store a collection of elements where each element points to the next element

• Stacks - used to store a collection of elements where the last element added is the first element removed

• Queues - used to store a collection of elements where the first element added is the first element removed

• Trees - used to store hiera...read more

I know multiple programming languages including Java, Python, and C++.

• Java

• Python

• C++

Static variable is a variable that retains its value even after the function execution is completed.

• Declared with static keyword

• Memory is allocated once and shared among all instances of the class or function

• Can be accessed without creating an object of the class

Triggers are database objects that are automatically executed in response to certain events.

• Triggers can be used to enforce business rules, audit changes, or replicate data.

• There are two types of triggers: DML triggers and DDL triggers.

• DML triggers are fired in response to DML statements (INSERT, UPDATE, DELETE).

• DDL triggers are fired in response to DDL statements (CREATE, ALTER, DROP).

Libraries and packages in Python are reusable collections of code that provide functionality to perform specific tasks.

• Libraries and packages help in reducing the amount of code that needs to be written from scratch

• Popular libraries in Python include NumPy for numerical computing, Pandas for data manipulation, and Matplotlib for data visualization

• Packages can be installed using package managers like pip or conda

Run time polymorphism is the ability of a program to determine the object type at runtime and call the appropriate method.

• It is achieved through virtual functions and dynamic binding.

• Allows for more flexible and extensible code.

• Example: a base class Animal with virtual function makeSound() and derived classes Dog and Cat that override makeSound().

• At runtime, if an Animal pointer points to a Dog object, calling makeSound() will execute the Dog's implementation.

Five commonly used Linux commands

• ls - list directory contents

• cd - change directory

• mkdir - make directory

• rm - remove files or directories

• grep - search for a pattern in a file

Query for deleting data from a database table.

• Use the DELETE statement followed by the table name.

• Add a WHERE clause to specify the condition for deleting specific rows.

• Be careful when deleting data as it cannot be recovered.

• Example: DELETE FROM customers WHERE customer_id = 1234;

Time complexity refers to the amount of time taken by an algorithm to run as the input size increases.

• It measures the efficiency of an algorithm.

• It is usually expressed in Big O notation.

• An algorithm with a lower time complexity is more efficient than one with a higher time complexity.

Count the number of vowels in a given string

• Iterate through each character in the string and check if it is a vowel (a, e, i, o, u)

• Maintain a count of vowels encountered

• Return the total count of vowels in the string

A copy constructor is a special type of constructor which creates a new object as a copy of an existing object.

• Ensure the copy constructor has the same signature as the default constructor.

• Allocate memory for the new object and copy the values from the existing object.

• Handle deep copy vs shallow copy based on the object's data types.

A copy constructor is a special type of constructor in object-oriented programming that creates a new object as a copy of an existing object.

• Creates a new object by copying the attributes of an existing object

• Used to initialize a new object with the values of an existing object

• Helps in creating deep copies of objects to avoid shallow copy issues

Object-oriented programming paradigm in Java focusing on objects and classes.

• OOPs stands for Object-Oriented Programming.

• It focuses on creating objects that interact with each other through classes.

• Key principles include Inheritance, Encapsulation, Polymorphism, and Abstraction.

• Example: Class Car { String color; void start() { //code here } }

• Example: Car myCar = new Car(); myCar.color = 'red'; myCar.start();

Collection framework in Java provides a set of interfaces and classes to store and manipulate groups of objects.

• Includes interfaces like List, Set, and Map

• Classes like ArrayList, LinkedList, HashSet, and HashMap implement these interfaces

• Provides methods for adding, removing, and accessing elements in collections

Count the number of occurrences of a specific substring in an array of strings.

• Iterate through each string in the array and use a function to count occurrences of the substring.

• Use a loop to go through each character in the string and check for matches with the substring.

• Keep a count variable to track the number of occurrences found.

Joins are used in databases to combine rows from two or more tables based on a related column between them.

• Joins are used to retrieve data from multiple tables based on a related column.

• Common types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.

• INNER JOIN returns rows when there is at least one match in both tables.

• LEFT JOIN returns all rows from the left table and the matched rows from the right table.

• RIGHT JOIN returns all rows from the right table and t...read more