700+ Full Stack Developer Interview Questions and Answers

Q1. Query and Matrix Problem Statement

You are given a binary matrix with 'M' rows and 'N' columns, initially consisting of all 0s. You will receive 'Q' queries, which can be of four types:

Query 1: 1 R index
Query ...read more

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 order. If n...read more

Q3. Most Frequent Non-Banned Word Problem Statement

Given a paragraph consisting of letters in both lowercase and uppercase, spaces, and punctuation, along with a list of banned words, your task is to find the most...read more

Q4. Count Substrings with K Distinct Characters

Given a lowercase string 'STR' and an integer K, the task is to count all possible substrings that consist of exactly K distinct characters. These substrings are not ...read more

Q6. Maximum Difference Problem Statement

Given an array ARR of N elements, your task is to find the maximum difference between any two elements in ARR.

If the maximum difference is even, print EVEN; if it is odd, p...read more

Q8. Count Set Bits Problem Statement

Given a positive integer N, compute the total number of '1's in the binary representation of all numbers from 1 to N. Return this count modulo 1e9+7 because the result can be ve...read more

Q9. Friends Pairing Problem

The task is to determine the total number of ways to pair up 'N' friends or leave some of them single, following these rules:

1. Each friend can either pair with one other friend or stay s...read more

Q10. 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

Q11. Distinct Strings With Odd and Even Swapping Allowed Problem Statement

You are provided with an array of strings, and your objective is to determine the number of unique strings within it.

A string is deemed uni...read more

Q12. Minimum Operations Problem Statement

You are given an array 'ARR' of size 'N' consisting of positive integers. Your task is to determine the minimum number of operations required to make all elements in the arr...read more

Q14. Sub Sort Problem Statement

You are given an integer array ARR. Determine the length of the shortest contiguous subarray which, when sorted in ascending order, results in the entire array being sorted in ascendi...read more

Q15. Longest Substring Without Repeating Characters Problem Statement

Given a string S of length L, determine the length of the longest substring that contains no repeating characters.

Example:

Input:

"abacb"

Output...read more

Q16. Excel Sheet Column Number Problem Statement

You are provided with a string STR representing a column title in an Excel Sheet. Your task is to determine the corresponding column number.

Example:

A typical exampl...read more

Q17. Ways To Make Coin Change

Given an infinite supply of coins of varying denominations, determine the total number of ways to make change for a specified value using these coins. If it's not possible to make the c...read more

Q18. Find a Node in Linked List

Given a singly linked list of integers, your task is to implement a function that returns the index/position of an integer value 'N' if it exists in the linked list. Return -1 if the ...read more

Q19. Matrix Rank Calculation

Given a matrix ARR of dimensions N * M, your task is to determine the rank of the matrix ARR.

Explanation:

The rank of a matrix is defined as:

(a) The maximum number of linearly independ...read more

Q20. Maximum Distance Problem Statement

Given an integer array 'A' of size N, your task is to find the maximum value of j - i, with the restriction that A[i] <= A[j], where 'i' and 'j' are indices of the array.

Inpu...read more

Q21. Rearrange String Problem Statement

Given a string ‘S’, your task is to rearrange its characters so that no two adjacent characters are the same. If it's possible, return any such arrangement, otherwise return “...read more

Q22. Add Two Numbers as Linked Lists

You are given two singly linked lists, where each list represents a positive number without any leading zeros.

Your task is to add these two numbers and return the sum as a linke...read more

Q23. Count Inversions Problem Statement

Given an integer array ARR of size N, your task is to find the total number of inversions that exist in the array.

An inversion is defined for a pair of integers in the array ...read more

Q24. Find All Pairs Adding Up to Target

Given an array of integers ARR of length N and an integer Target, your task is to return all pairs of elements such that they add up to the Target.

Input:

The first line conta...read more

Q25. Sort 0 1 2 Problem Statement

Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.

Input:

The first line contains an integer 'T' representing the number of...read more

Q26. Relative Sorting Problem Statement

You are given two arrays, 'ARR' of size 'N' and 'BRR' of size 'M'. Your task is to sort the elements of 'ARR' such that their relative order matches that in 'BRR'. Any element...read more

Q27. Alternating Largest Problem Statement

Given a list of numbers, rearrange them such that every second element is greater than its adjacent elements. Implement a function to achieve this rearrangement.

Input:

The...read more

Q28. LCA in a Binary Search Tree

You are given a binary search tree (BST) containing N nodes. Additionally, you have references to two nodes, P and Q, within this BST.

Your task is to determine the Lowest Common Anc...read more

Q29. Make Array Elements Equal Problem Statement

Given an integer array, your objective is to change all elements to the same value, minimizing the cost. The cost of changing an element from x to y is defined as |x ...read more

Q30. Minimum Characters to Make a String Palindrome

Given a string STR of length N, determine the minimum number of characters to be added to the front of the string to make it a palindrome.

Input:

The first line co...read more

Q31. Ceil Value from BST Problem Statement

Given a Binary Search Tree (BST) and an integer, write a function to return the ceil value of a particular key in the BST.

The ceil of an integer is defined as the smallest...read more

Q32. Reverse Integer Problem Statement

Given a 32-bit signed integer N, your task is to return the reversed integer. If reversing the integer causes overflow, return -1.

Input:

The first line contains an integer 'T'...read more

Q33. Factorial of a Number Problem Statement

You are provided with an integer 'N'. Your task is to calculate and print the factorial of 'N'. The factorial of a number 'N', denoted as N!, is the product of all positi...read more

Q34. Find Indices for Local Minima and Maxima

Given an integer array arr of size N, your task is to determine all indices of local minima and local maxima within the array. Return these indices in a 2-D list, where ...read more

Q35. LRU Cache Design Question

Design a data structure for a Least Recently Used (LRU) cache that supports the following operations:

1. get(key) - Return the value of the key if it exists in the cache; otherwise, re...read more

Q36. Anagram Pairs Verification Problem

Your task is to determine if two given strings are anagrams of each other. Two strings are considered anagrams if you can rearrange the letters of one string to form the other...read more

Q37. Count Ways to Reach the N-th Stair Problem Statement

You are provided with a number of stairs, and initially, you are located at the 0th stair. You need to reach the Nth stair, and you can climb one or two step...read more

Q38. Find Duplicate in Array Problem Statement

You are provided with an array of integers 'ARR' consisting of 'N' elements. Each integer is within the range [1, N-1], and the array contains exactly one duplicated el...read more

Q39. Longest Common Prefix Problem Statement

You are given an array ‘ARR’ consisting of ‘N’ strings. Your task is to find the longest common prefix among all these strings. If there is no common prefix, you have to ...read more

Q40. Maximum Consecutive Ones Problem Statement

Given a binary array 'ARR' of size 'N', your task is to determine the maximum length of a sequence consisting solely of 1’s that can be obtained by converting at most ...read more

Q41. Rotate Matrix by 90 Degrees Problem Statement

Given a square matrix 'MATRIX' of non-negative integers, rotate the matrix by 90 degrees in an anti-clockwise direction using only constant extra space.

Input:

The ...read more

Q42. Subtree of Another Tree Problem Statement

Given two binary trees, T and S, determine whether S is a subtree of T. The tree S should have the same structure and node values as a subtree of T.

Explanation:

A subt...read more

Array Sum Calculation

Calculate the sum of all elements in an array of length N.

Input:

Line 1: An integer N indicating the size of the array.
Line 2: N integers, the elements of the array, separated by spaces.

Q44. Check Permutation Problem Statement

Determine if two given strings, 'str1' and 'str2', are permutations of each other.

Explanation:

Two strings are permutations of each other if one string's characters can be r...read more

Q45. Find the Third Greatest Element

Given an array 'ARR' of 'N' distinct integers, determine the third largest element in the array.

Input:

The first line contains a single integer 'T' representing the number of te...read more

Q46. N Queens Problem

Given an integer N, find all possible placements of N queens on an N x N chessboard such that no two queens threaten each other.

Explanation:

A queen can attack another queen if they are in the...read more

Q47. Rotational Equivalence of Strings Problem Statement

Given two strings 'P' and 'Q' of equal length, determine if string 'P' can be transformed into string 'Q' by cyclically rotating it to the right any number of...read more

Q49. Number of Islands II Problem Statement

You have a 2D grid of dimensions 'N' rows by 'M' columns, initially filled with water. You are given 'Q' queries, where each query contains two integers 'X' and 'Y'. Durin...read more

Q50. Smallest Number with Given Digit Product

Given a positive integer 'N', find and return the smallest number 'M', such that the product of all the digits in 'M' is equal to 'N'. If such an 'M' is not possible or ...read more