Full Stack Engineer

20+ Full Stack Engineer Interview Questions and Answers for Freshers

Updated 10 May 2024
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Q1. Find All Subsets

Given an array arr consisting of 'N' distinct integers, your task is to generate all possible non-empty subsets of the given array.

You can return the subsets in any order.

Input:

The first lin...read more
Ans.

Generate all possible non-empty subsets of a given array of distinct integers.

  • Use recursion to generate all subsets by including or excluding each element in the array.

  • Maintain a current subset and iterate through the array to generate subsets.

  • Print each subset as it is generated to get all possible non-empty subsets.

Q2. Longest Palindromic Subsequence Problem Statement

Given a string A consisting of lowercase English letters, determine the length of the longest palindromic subsequence within A.

Explanation:

  • A subsequence is d...read more
Ans.

The task is to find the length of the longest palindromic subsequence in a given string.

  • Iterate through the string and create a 2D array to store the lengths of palindromic subsequences.

  • Use dynamic programming to fill the array based on the characters in the string.

  • Consider the cases where characters match or do not match to update the array values.

  • Return the length of the longest palindromic subsequence for each test case.

Q3. Word Pattern Problem Statement

Given two strings S and T, determine if S follows the same pattern as T.

A full match means there is a bijection between a letter of T and a non-empty word of S.

Example:

Input:
S...read more
Ans.

Check if two strings follow the same pattern based on bijection between letters and words.

  • Iterate through each letter in T and corresponding word in S to create a mapping.

  • Use a hashmap to store the mapping between letters and words.

  • Check if the mapping is consistent for all test cases.

Q4. Reverse Linked List Problem Statement

Given a singly linked list of integers, return the head of the reversed linked list.

Example:

Initial linked list: 1 -> 2 -> 3 -> 4 -> NULL
Reversed linked list: 4 -> 3 -> 2...read more
Ans.

Reverse a singly linked list of integers and return the head of the reversed linked list.

  • Iterate through the linked list and reverse the pointers to point to the previous node instead of the next node.

  • Keep track of the current, previous, and next nodes while traversing the linked list.

  • Update the head of the reversed linked list to be the last node encountered.

  • Ensure to handle edge cases like an empty linked list or a single node in the list.

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Q5. Next Smallest Palindrome Problem Statement

Given a string representation of a number 'S', determine the smallest palindrome that is strictly greater than this number 'N'.

Example:

Input:
3
2
99
3
123
4
4567
Output:
1...read more
Ans.

The task is to find the smallest palindrome greater than a given number.

  • Iterate from the middle of the number and mirror the left side to form the palindrome.

  • Handle cases where the number is already a palindrome or has all 9s.

  • Consider odd and even length numbers separately.

  • Convert the string to integer for comparison and manipulation.

Q6. Level Order Traversal Problem Statement

Given a binary tree of integers, return the level order traversal of the binary tree.

Input:

The first line contains an integer 'T', representing the number of test cases...read more
Ans.

Implement a function to return the level order traversal of a binary tree of integers.

  • Create a queue to store nodes for level order traversal

  • Start with the root node and enqueue it

  • While the queue is not empty, dequeue a node, print its value, and enqueue its children

  • Repeat until all nodes are traversed

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Q7. Maximum Size Rectangle Sub-matrix with All 1's Problem Statement

You are provided with an N * M sized binary matrix 'MAT' where 'N' denotes the number of rows and 'M' denotes the number of columns. Your task is...read more

Ans.

The task is to find the maximum size of a submatrix consisting of all 1's in a given binary-valued matrix.

  • Iterate through each cell of the matrix

  • For each cell, calculate the maximum size of a submatrix with that cell as the top-left corner

  • Keep track of the maximum size encountered so far

  • Return the maximum size

Q8. Count Subarrays with Sum Divisible by K

Given an array ARR and an integer K, your task is to count all subarrays whose sum is divisible by the given integer K.

Input:

The first line of input contains an integer...read more
Ans.

Count the number of subarrays in an array whose sum is divisible by a given integer K.

  • Iterate through the array and keep track of the running sum modulo K.

  • Use a hashmap to store the frequency of remainders.

  • For each prefix sum, check how many previous prefix sums have the same remainder.

  • Return the total count of subarrays with sum divisible by K.

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Q9. Smaller Elements Count Problem Statement

Given an array of size N, return a count array such that COUNT[i] equals the number of elements which are smaller than ARR[i] on its right side.

Input:

Input Format:
The...read more
Ans.

Return an array where each element represents the count of smaller elements on its right side in the given array.

  • Iterate through the array from right to left and maintain a sorted list of elements encountered so far.

  • For each element, find its index in the sorted list to determine the count of smaller elements on its right side.

  • Use binary search or segment trees for efficient searching and updating of the sorted list.

Q10. Count the Number of Ones Problem Statement

Given an integer N, calculate the total number of times the digit '1' appears in each number from 0 to N inclusive.

Input:

T (number of test cases)
Each test case conta...read more
Ans.

The task is to count the number of occurrences of the digit '1' in each number from 0 to N.

  • Iterate through each number from 0 to N

  • Convert each number to a string

  • Count the number of occurrences of the digit '1' in the string representation of each number

  • Return the total count of '1's

Q11. Next Greater Node in Linked List Problem Statement

In a set of linked ninja villages, the goal is to determine if a stronger ninja exists in the nearest village linked ahead. Given a linked list of 'N' integers...read more

Ans.

Given a linked list of ninja villages, find the next greater ninja strength in the nearest linked village.

  • Traverse the linked list and store the elements in an array.

  • Use a stack to keep track of elements with no next greater element found yet.

  • Iterate through the array to find the next greater element for each village.

  • Return the array of next greater elements for each village.

Q12. Minimum Operations to Equalize Array

Given an integer array ARR of length N where ARR[i] = (2*i + 1), determine the minimum number of operations required to make all the elements of ARR equal. In a single opera...read more

Ans.

The minimum number of operations required to make all elements of the given array equal.

  • The array is generated based on the formula ARR[i] = (2*i + 1).

  • To equalize the array, increment one element and decrement another in each operation.

  • The number of operations needed is equal to the difference between the maximum and minimum elements in the array.

Q13. Rank from Stream Problem Statement

Given an array of integers ARR and an integer K, determine the rank of the element ARR[K].

Explanation:

The rank of any element in ARR is defined as the number of elements sma...read more

Ans.

The task is to determine the rank of a specific element in an array based on the number of smaller elements before it.

  • Iterate through the array up to index K and count the number of elements smaller than ARR[K].

  • Return the count as the rank of ARR[K].

  • Handle multiple test cases by repeating the process for each case.

Q14. 0/1 Knapsack Problem Statement

A thief is planning to rob a store and can carry a maximum weight of 'W' in his knapsack. The store contains 'N' items where the ith item has a weight of 'wi' and a value of 'vi'....read more

Ans.

The 0/1 Knapsack Problem involves maximizing the total value of items a thief can steal within a given weight limit.

  • Dynamic programming can be used to solve this problem efficiently.

  • Create a 2D array to store the maximum value that can be stolen at each weight capacity.

  • Iterate through the items and update the array based on whether the item is included or not.

  • The final answer will be the value at the last cell of the array.

Q15. Count Distinct Substrings

You are provided with a string S. Your task is to determine and return the number of distinct substrings, including the empty substring, of this given string. Implement the solution us...read more

Ans.

Implement a function to count the number of distinct substrings in a given string using a trie data structure.

  • Create a trie data structure to store the substrings of the input string.

  • Traverse the trie to count the number of distinct substrings.

  • Handle empty string as a distinct substring.

  • Return the count of distinct substrings for each test case.

Q16. Edit Distance Problem Statement

Given two strings S and T with lengths N and M respectively, your task is to find the "Edit Distance" between these strings.

The Edit Distance is defined as the minimum number of...read more

Ans.

The task is to find the minimum number of operations required to convert one string into another using delete, replace, and insert operations.

  • Use dynamic programming to solve the problem efficiently.

  • Create a 2D array to store the edit distances between substrings of the two input strings.

  • Fill up the array based on the minimum of three possible operations: insert, delete, or replace.

  • Return the value at the bottom right corner of the array as the final edit distance.

Q17. Merge Intervals Problem Statement

You are provided with 'N' intervals, each containing two integers denoting the start time and end time of the interval.

Your task is to merge all overlapping intervals and retu...read more

Ans.

Merge overlapping intervals and return sorted list by start time.

  • Sort the intervals based on start time.

  • Iterate through intervals and merge overlapping ones.

  • Return the merged intervals sorted by start time.

Q18. Longest Subarray Zero Sum Problem Statement

Given an array of integers arr, determine the length of the longest contiguous subarray that sums to zero.

Input:

N (an integer, the length of the array)
arr (list of ...read more
Ans.

Find the length of the longest contiguous subarray that sums to zero in an array of integers.

  • Iterate through the array and keep track of the running sum and its corresponding index in a hashmap.

  • If the running sum is seen again, calculate the length of the subarray by subtracting the current index from the index stored in the hashmap.

  • Update the maximum length of the subarray as you iterate through the array.

Q19. Can you provide examples of OOP concepts using code, including coding for all the principles of Object-Oriented Programming?
Ans.

Examples of OOP concepts using code and principles

  • Encapsulation: Using private variables and getter/setter methods

  • Inheritance: Creating subclasses that inherit properties and methods from a superclass

  • Polymorphism: Implementing methods with the same name but different functionality in subclasses

Q20. What is API? Difference between API and RestApi What is cloud? Where have you used cloud till now? Database related questions. A few html js related questions.

Ans.

API stands for Application Programming Interface. It defines the methods and data formats that applications can use to communicate with each other.

  • API is a set of rules and protocols that allows different software applications to communicate with each other.

  • REST API is a type of API that follows the principles of REST (Representational State Transfer) architecture.

  • Cloud computing refers to the delivery of computing services over the internet, including storage, databases, net...read more

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