Persistent Systems Node JS Developer Interview Questions and Answers for Experienced

Round duration - 45 Minutes
Round difficulty - Easy

The round was conducted at 12 in the college campus. It was a pen and paper based coding round and had 2 coding questions for which we had to write the best approach.

Q1. 
Equilibrium Index Problem Statement
Given an array Arr consisting of N integers, your task is to find the equilibrium index of the array.
An index is considered as an equilibrium index if the sum of elem...read more
Ans. 
Find the equilibrium index of an array where sum of elements on left equals sum on right.
• Iterate through the array and calculate the total sum of all elements.

• Then iterate again and keep track of the left sum and right sum, checking for equilibrium.

• Return the index when left sum equals right sum, or -1 if no equilibrium index found.
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Q2. 
Merge Sort Linked List Problem Statement
You are given a singly linked list of integers. Your task is to sort the linked list using the merge sort algorithm.
Explanation:
Merge Sort is a divide and conq...read more
Ans. 
Implement merge sort algorithm to sort a singly linked list of integers.
• Divide the linked list into two halves using slow and fast pointers.

• Recursively sort the two halves.

• Merge the sorted halves using a merge function.

• Handle base cases like empty list or single node list.

• Ensure the termination of the linked list with -1 at the end.
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Round duration - 45 Minutes
Round difficulty - Easy

There were 2 coding questions and we had to write the best approach for the questions.

Q1. 
Convert Sentence Problem Statement
Convert a given string 'S' into its equivalent representation based on a mobile numeric keypad sequence. Using the keypad layout shown in the reference, output the seque...read more
Ans. 
Convert a given string into its equivalent representation based on a mobile numeric keypad sequence.
• Create a mapping of characters to their corresponding numeric keypad sequences.

• Iterate through the input string and append the numeric sequence for each character to the output.

• Handle lowercase characters only, ignore special characters, capital letters, and spaces in the input string.
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Q2. 
Subsequences of String Problem Statement
You are provided with a string 'STR' that consists of lowercase English letters ranging from 'a' to 'z'. Your task is to determine all non-empty possible subsequen...read more
Ans. 
Generate all possible subsequences of a given string.
• Use recursion to generate all possible subsequences by including or excluding each character in the string.

• Maintain a current index to keep track of the characters being considered.

• Append the current character to each subsequence generated so far.

• Recursively call the function with the next index to include the next character in subsequences.
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Round duration - 40 minutes
Round difficulty - Easy

The interviewer asked me questions from arrays, strings and linked list.

Q1. 
Longest Increasing Subsequence Problem Statement
Given an array of integers with 'N' elements, determine the length of the longest subsequence where each element is greater than the previous element. This...read more
Ans. 
Find the length of the longest strictly increasing subsequence in an array of integers.
• Use dynamic programming to keep track of the longest increasing subsequence ending at each element.

• Initialize an array to store the lengths of the longest increasing subsequences.

• Iterate through the array and update the lengths based on the previous elements.

• Return the maximum length found in the array.
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Q2. 
Binary Palindrome Check
Given an integer N, determine whether its binary representation is a palindrome.
Input:
The first line contains an integer 'T' representing the number of test cases. 
The next 'T'...read more
Ans. 
Check if the binary representation of a given integer is a palindrome.
• Convert the integer to binary representation.

• Check if the binary representation is a palindrome by comparing it with its reverse.

• Return true if it is a palindrome, false otherwise.
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