Presidio Solutions Pvt Ltd Full Stack Software Developer Interview Questions and Answers for Freshers

Round duration - 40 minutes
Round difficulty - Medium

Asked about time complexity of algorithm, puzzles, DBMS, cutting edge technologies etc. What are indexes?

Q1. 
Flip Bits Problem Explanation
Given an array of integers ARR of size N, consisting of 0s and 1s, you need to select a sub-array and flip its bits. Your task is to return the maximum count of 1s that can b...read more
Ans. 
Given an array of 0s and 1s, find the maximum count of 1s by flipping a sub-array at most once.
• Iterate through the array and keep track of the maximum count of 1s obtained by flipping a sub-array.

• Consider flipping a sub-array from index i to j and calculate the count of 1s in the resulting array.

• Return the maximum count of 1s obtained by flipping a sub-array at most once.
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Round duration - 20 minutes
Round difficulty - Medium

Asked 1 standard algorithm

Q1. 
Number of Islands Problem Statement
You are provided with a 2-dimensional matrix having N rows and M columns, containing only 1s (land) and 0s (water). Your goal is to determine the number of islands in t...read more
Ans. 
Count the number of islands in a 2D matrix of 1s and 0s.
• Iterate through the matrix and perform depth-first search (DFS) to find connected 1s.

• Mark visited cells to avoid redundant traversal.

• Increment island count whenever a new island is encountered.
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Round duration - 90 minutes
Round difficulty - Easy

There were two section Aptitude and Coding.

Q1. 
Buy and Sell Stock Problem Statement
Imagine you are Harshad Mehta's friend, and you have been given the stock prices of a particular company for the next 'N' days. You can perform up to two buy-and-sell ...read more
Ans. 
The task is to determine the maximum profit that can be achieved by performing up to two buy-and-sell transactions on a given set of stock prices.
• Iterate through the array of stock prices and calculate the maximum profit that can be achieved by buying and selling at different points.

• Keep track of the maximum profit after the first transaction and the maximum profit overall by considering different combinations of buy a...read more
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Round duration - 60 minutes
Round difficulty - Easy

This was the first technical interview.

Q1. 
Pair Sum Problem Statement
You are given an integer array 'ARR' of size 'N' and an integer 'S'. Your task is to find and return a list of all pairs of elements where each sum of a pair equals 'S'.
Note:
...read more
Ans. 
Find pairs of elements in an array that sum up to a given value, sorted in a specific order.
• Iterate through the array and for each element, check if the complement (S - current element) exists in a hash set.

• Keep track of pairs in a hash set to avoid duplicates.

• Sort the pairs based on the criteria mentioned in the question.

• Return the sorted list of pairs.
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Round duration - 120 minutes
Round difficulty - Medium

Timing was 9: 30 AM. Platform was quite good and easy to understand.

Q1. 
Reverse Only Letters Problem Statement
You are given a string S. The task is to reverse the letters of the string while keeping non-alphabet characters in their original position.
Example:
Input:
S = "...read more
Ans. 
Reverse the letters of a string while keeping non-alphabet characters in their original position.
• Iterate through the string and maintain two pointers, one at the start and one at the end, to reverse only the letters

• Use isalpha() function to check if a character is an alphabet or not

• Swap the letters at the two pointers until they meet in the middle
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Q2. 
Find Duplicates in an Array
Given an array ARR of size 'N', where each integer is in the range from 0 to N - 1, identify all elements that appear more than once.
Return the duplicate elements in any orde...read more
Ans. 
Find duplicates in an array of integers within a specified range.
• Iterate through the array and keep track of the count of each element using a hashmap.

• Return elements with count greater than 1 as duplicates.

• Time complexity can be optimized to O(N) using a set to store duplicates.

• Example: For input [0, 3, 1, 2, 3], output should be [3].
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Q3. 
Pancake Sorting Problem Statement
You are given an array of integers 'ARR'. Sort this array using a series of pancake flips. In each pancake flip, you need to:
Choose an integer 'K' where 1 <= 'K' <...read more
Ans. 
Sort an array using pancake flips and return the sequence of flips made.
• Iterate through the array and find the position of the maximum element in each iteration.

• Perform pancake flips to move the maximum element to the correct position.

• Continue this process until the array is sorted.

• Return the sequence of positions from where flips were made.
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Q4. 
Sum of Digits Problem Statement
Given an integer 'N', continue summing its digits until the result is a single-digit number. Your task is to determine the final value of 'N' after applying this operation ...read more
Ans. 
Given an integer, find the final single-digit value after summing its digits iteratively.
• Iteratively sum the digits of the given integer until the result is a single-digit number

• Output the final single-digit integer for each test case

• Handle multiple test cases efficiently
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Round duration - 30 minutes
Round difficulty - Medium

Timing was 9:30 AM. The interviewer was very nice.

Q1. 
Fibonacci Number Verification
Identify if the provided integer 'N' is a Fibonacci number.
A number is termed as a Fibonacci number if it appears in the Fibonacci sequence, where each number is the sum of...read more
Ans. 
Check if a given number is a Fibonacci number or not.
• Iterate through the Fibonacci sequence until you find a number greater than or equal to the given number.

• Check if the given number matches the Fibonacci number found in the sequence.

• If the number matches, output 'YES'; otherwise, output 'NO'.
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Q2. Write an SQL query to find the second highest salary from a table.
Ans. 
SQL query to find the second highest salary from a table
• Use the MAX() function to find the highest salary

• Use the WHERE clause to exclude the highest salary

• Order the salaries in descending order and limit the result to 1
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Round duration - 30 Minutes
Round difficulty - Medium

Timing was 12 PM. Interviewer was not good.

Q1. 
Character Frequency Problem Statement
You are given a string 'S' of length 'N'. Your task is to find the frequency of each character from 'a' to 'z' in the string.
Example:
Input:
S : abcdg
Output:
1...read more
Ans. 
The task is to find the frequency of each character from 'a' to 'z' in a given string.
• Create an array of size 26 to store the frequency of each character from 'a' to 'z'.

• Iterate through the string and increment the count of the corresponding character in the array.

• Print the array of frequencies as the output for each test case.
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Q2. What is normalization and can you explain the concept of Third Normal Form (3NF)?
Ans. 
Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity.
• Normalization is a technique used to organize data in a database efficiently.

• Third Normal Form (3NF) is a level of normalization that ensures that data is stored in a way that prevents certain types of data anomalies.

• In 3NF, every non-prime attribute is fully functionally dependent on the primary key.

• For exampl...read more
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