Cognizant Junior Java Developer Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Easy

This was an easy round which went really smooth.

Q1. 
Nth Fibonacci Number Problem Statement
Calculate the Nth term in the Fibonacci sequence, where the sequence is defined as follows: F(n) = F(n-1) + F(n-2), with initial conditions F(1) = F(2) = 1.
Input:
...read more
Ans. 
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 iteratively calculate F(n) using F(n-1) and F(n-2).

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

• Example: For N = 5, the 5th Fibonacci number is 5 (1, 1, 2, 3, 5).
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Q2. 
Prime Numbers Problem Statement
Given a positive integer N, your task is to determine and return all prime numbers less than or equal to N.
Input:
N = 10
Output:
2 3 5 7
Example:
Input:
N = 20
Out...read more
Ans. 
Implement a function to return all prime numbers less than or equal to a given positive integer N.
• Create a function that takes a positive integer N as input

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

• Use a helper function to determine if a number is prime

• Return an array of all prime numbers less than or equal to N
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Q3. What is a merge join in SQL?
Ans. 
A merge join in SQL is a method of combining two sorted datasets by matching corresponding rows based on a specified condition.
• Merge join is used when joining two large datasets that are already sorted.

• It is more efficient than other join methods like nested loop join or hash join for sorted datasets.

• The join condition must be an equality condition.

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.id = table2.i
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Round duration - 30 minutes
Round difficulty - Easy

The round went excellent. I really enjoyed it. Just be confident about whatever you answer

Round duration - 60 minutes
Round difficulty - Easy

This round went well. Interview depends on your basic knowledge of C/C++.

Q1. 
Matrix Multiplication Task
Given two sparse matrices MAT1 and MAT2 of integers with dimensions 'N' x 'M' and 'M' x 'P' respectively, the goal is to determine the resulting matrix produced by their multipl...read more
Ans. 
Implement a function to multiply two sparse matrices and return the resulting matrix.
• Create a function that takes two sparse matrices as input and returns the resulting matrix after multiplication

• Iterate through the non-zero elements of the matrices to perform the multiplication efficiently

• Handle the edge cases such as empty matrices or matrices with all zero elements

• Ensure the dimensions of the matrices are compatible
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Q2. 
Problem: Count Even or Odd in Array
Tanmay and Rohit are best buddies. Tanmay gives Rohit a challenge involving an array of N natural numbers. The task is to perform and answer a series of queries on the ...read more
Ans. 
Count the number of even or odd numbers in a range of an array based on given queries.
• Create an array to store the input numbers.

• Iterate through the queries and update or count even/odd numbers based on the query type.

• Output the count of even or odd numbers for each query of type 1 or 2.
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Round duration - 30 minutes
Round difficulty - Easy

Typical HR round with behavioral problems.