700+ Thought Frameworks Interview Questions and Answers

Q1. Buses

You are given a vector of 'N' integers denoting the number of buses that can be boarded from the i-th position. The bus stops only at stops whose number is a multiple of the bus stop number from which the ...read more

Q2. 9268 | Chess Tournament

Chess tournament is going to be organized in Ninjaland. There will be C chess players going to attend the tournament. All the players will be staying in a hotel. The hotel has N free room...read more

Q3. Day of the Week

Write a function that calculates the corresponding day of the week for any particular date in the past or future.

For example, for the date 28th August 2020 happens to be Friday. Hence the expect...read more

Q4. Fruits and Baskets

There are ‘n’ fruit trees that are planted along a road. The trees are numbered from 0 to n-1. The type of fruit each tree bears is represented by an uppercase character of the English alphabe...read more

Q5. Check If One String Is A Rotation Of Another String

You are given two Strings 'P' and 'Q' of equal length. Your task is to check whether String 'P' can be converted into String 'Q' by cyclically rotating it to t...read more

Q6. The Celebrity Problem

There are ‘N’ people at a party. Each person has been assigned a unique id between 0 to 'N' - 1(both inclusive). A celebrity is a person who is known to everyone but does not know anyone at...read more

Q7. Longest Mountain Subarray

You are given an array of 'N' integers denoting the heights of the mountains. You need to find the length of the longest subarray which has the shape of a mountain.

A mountain subarray ...read more

Q9. Data Structure Supporting Insert Delete And GetRandom

Design and implement a data structure which supports the following operations:

insert(X): Inserts an element X in the data structure and returns true if the ...read more

Q10. Nth term of gp series

You are given the first term (A), the common ratio (R) and an integer N. Your task is to find the Nth term of the GP series.

The general form of a GP(Geometric Progression) series is A, A(R...read more

Q11. Word Wrap

You are given ‘N’ words of various lengths, now you have to arrange these words in such a way that each line contains at most ‘M’ characters and each word is separated by a space character. The cost of...read more

Q12. Find all triplets with zero sum

You are given an array Arr consisting of n integers, you need to find all the distinct triplets present in the array which adds up to zero.

An array is said to have a triplet {arr...read more

Q13. Distinct Strings With Odd and Even Swapping Allowed

You are given an array of strings. Your task is to find the number of unique strings.

A string is considered unique if it cannot be formed from any other strin...read more

Q14. Kth largest element in the unsorted array

You are given an array consisting of 'N' distinct positive integers and a number 'K'. Your task is to find the kth largest element in the array.

Example:

Consider the ar...read more

Q15. Dice throw

You are given D dice, each having F faces numbered 1 to F, both inclusive. The task is to find the possible number of ways to roll the dice together such that the sum of face-up numbers equal the give...read more

Q16. Generate all binary strings from pattern

You're given a string 'STR' containing ‘0’, ‘1’ and ‘?’ special characters. Your task is to generate all the strings that are possible by replacing the special character ...read more

Q17. Sum of leaf nodes at maximum level

You have been given a binary tree of integers. Your task is to calculate the sum of all the leaf nodes which are present at the deepest level of this binary tree. If there are ...read more

Q18. Palindrome Linked List

You are given a singly Linked List of integers. Your task is to return true if the given singly linked list is a palindrome otherwise returns false.

For example:

The given linked list is 1...read more

Q19. Total Strings

You are given a positive integer 'N'. Your task is to find the number of strings of length ‘N’ that can be formed using only the characters ‘a’, ‘b’ and ‘c’. The strings formed should be such that ...read more

Q20. Maximum Subarray Sum

You are given an array (ARR) of length N, consisting of integers. You have to find the sum of the subarray (including empty subarray) having maximum sum among all subarrays.

A subarray is a...read more

Q21. First Missing Positive

You are given an array 'ARR' of integers of length N. Your task is to find the first missing positive integer in linear time and constant space. In other words, find the lowest positive in...read more

Q22. Find K’th Character of Decrypted String

You have been given an Encrypted String where repetitions of substrings are represented as substring followed by the count of substrings.

Example: String "aabbbcdcdcd" wi...read more

Q23. Rearrange string

You are given a string “S”. Your task is to rearrange the characters of a string “S”, such that it does not contain any two adjacent characters which are the same.

If it is possible to rearrange...read more

Q24. Buy and Sell Stock

You are Harshad Mehta’s friend. He told you the price of a particular stock for the next ‘N’ days. You can either buy or sell a stock. Also, you can only complete at most 2-transactions. Find...read more

Q25. Cycle Detection in a Linked List

You have given a Singly Linked List of integers, determine if it forms a cycle or not.

A cycle occurs when a node's next points back to a previous node in the list. The linked li...read more

Q26. Detect the first node of the loop

You have been given a singly linked list which may or may not contain a cycle. You are supposed to return the node where the cycle begins (if a cycle exists).

A cycle occurs whe...read more

Q27. Merge Sort

Given a sequence of numbers ‘ARR’. Your task is to return a sorted sequence of ‘ARR’ in non-descending order with help of the merge sort algorithm.

Example :

Merge Sort Algorithm - Merge sort is a Div...read more

Q28. Nearest Multiple of 10

You have been given an integer 'N'. Find the nearest multiple of 10 to the given integer 'N'.

Note:

If there are multiple answers, find the smallest one. For example, if N = 35, both 30 an...read more

Q29. Mean median mode of unsorted array

You are given an array 'ARR' of 'N' integers and you have to calculate 3 things for the given array:-

1. Mean - function mean(): This function should calculate the mean of the ...read more

Q30. Sum root to leaf

You are given an arbitrary binary tree consisting of N nodes where each node is associated with a certain integer value from 1 to 9. Consider each root to leaf path as a number.

For example:

 1 ...read more

Q31. Dice Throws

You are given D dice, each having F faces numbered 1 to F, both inclusive. The task is to find the possible number of ways to roll the dice together such that the sum of face-up numbers equal the giv...read more

Q32. Look-And-Say Sequence

The Look-And-Say sequence is a sequence of positive integers. The sequence is as follows:

1, 11, 21, 1211, 111221, 312211, 13112221,...

This sequence is constructed in the following way:

Th...read more

Q33. N Queens

You are given an integer 'N'. For a given 'N' x 'N' chessboard, find a way to place 'N' queens such that no queen can attack any other queen on the chessboard.

A queen can be killed when it lies in the ...read more

Q34. Flatten Binary Tree

You are given a binary tree consisting of integer values. Your task is to convert the given binary tree into a linked list where the nodes of the linked list follow the same order as the pre-...read more

Q35. Check if given words are present in a string

Given a string 'S' and a list 'wordList' that consists of 'N' distinct words. Let 'Wi' denote word at index 'i' in 'wordList'. For each word 'Wi' in 'wordList', you n...read more

Q36. IP Address

You are given a string “S” containing only digits from 0 to 9. Your task is to find all possible IP addresses that can be obtained from S in lexicographical order. If no valid IP address can be genera...read more

Q38. Distinct subsequences of an array

You have been given string 'S' of length 'N' that may contain duplicate alphabets. Your task is to return the count of distinct subsequences of it.

For example:

For the given st...read more

Q39. Add two numbers represented by linked lists

You have been given two singly Linked Lists, where each of them represents a positive number without any leading zeros.

Your task is to add these two numbers and print...read more

Q40. Find rank

You are given a matrix ‘ARR’ having dimensions ‘N*M’. Your task to find the rank of the matrix ‘ARR’.

The rank of a matrix is defined as:

(a) The maximum number of linearly independent column vectors i...read more

Q41. Rearrange Array Numbers to form Largest Possible Number

You are given an array(ARR) of length 'N', consisting of non-negative integers. Using only these given numbers, rearrange the numbers in such a way that th...read more

Q42. Word Break

You are given a list of “N” strings A. Your task is to check whether you can form a given target string using a combination of one or more strings of A.

Note :

You can use any string of A multiple tim...read more

Q43. Rooms

You are given some information about the rooms of a military camp. The rooms are numbered from 0 to 'N-1'. Each room contains keys to some other rooms. You can visit a room only if you have a key to that r...read more

Q44. Buying And Selling Stock

You have been given the prices of 'N' stocks in an array where each array element represents the stock price for that day. You need to find the maximum profit which you can make by buyin...read more

Q45. Construct Binary Tree From Inorder and Preorder Traversal

You have been given the preorder and inorder traversal of a binary tree. Your task is to construct a binary tree using the given inorder and preorder tra...read more

Q46. Maximum path sum between two leaves of a binary tree

You are given a non-empty binary tree where each node has a non-negative integer value. Return the maximum possible sum of path between any two leaves of the ...read more

Q47. Group Anagrams

You have been given an array/list of strings 'inputStr'. You are supposed to return the strings as groups of anagrams such that strings belonging to a particular group are anagrams of one another....read more

Q48. Given stock price array, find maximum profit if you are only allowed to buy and sell once. Input: [7,1,5,3,6,4] Output: 5

You are Harshad Mehta’s friend. He told you the price of a particular stock for the next ...read more

Q49. Delete N nodes after M nodes of a linked list

You have given a singly linked list and two integers 'N' and 'M'. Delete 'N' nodes after every 'M' node, or we can say more clearly that traverse the linked list suc...read more

Q50. Simplify the Directory

You are given a path to a file/directory in Unix-style of length N, In a Unix-style file system, a dot(.) refers to the current directory. A double dot(..) refers to the previous directory...read more

Q51. Gray Code

Given a number ‘grayNumber’. Find the gray code sequence.

Conditions for a gray code sequence :

1. Gray code sequence contains numbers from 0 to 2^'grayNumber'-1 in bit/binary form. 2. Two consecutive ...read more

Q52. Ninja And Alternating Largest

Ninja is given a few numbers, and he is being asked to rearrange the numbers so that every second element is greater than its left and right element.

Input Format:

The first line of...read more

Q53. Train collision puzzle

Two trains, separated by a distance of 80km, are running towards each other on the same track at a speed of 40 kmph. A bird takes its flight from train X and flies towards train Y at a con...read more

Q54. Running median

You are given a stream of 'N' integers. For every 'i-th' integer added to the running list of integers, print the resulting median.

Print only the integer part of the median.

Input Format :

The fi...read more

Q55. Ninja And The Tree

Ninja is learning tree data structure these days. While learning, she came across learn about the Binary Search tree. She found BST quite interesting. She decided to make her own Binary Search...read more

Q56. Count Inversions

Let A[0 ... n-1] be an array of n distinct positive integers. If i < j and A[i] > A[j] then the pair (i, j) is called an inversion of A (where i and j are indexes of A). Given an integer array A...read more

Q57. Time to Burn Tree

You have been given a binary tree of 'N' unique nodes and a Start node from where the tree will start to burn. Given that the Start node will always exist in the tree, your task is to print the...read more

Q58. Kth Smallest Element

You are given an array of integers 'ARR' of size 'N' and another integer 'K'. Your task is to find and return 'K'th smallest value present in the array.

Note: All the elements in the array a...read more

Q59. Intersection of Linked Lists

There are two singly linked lists in a system. By some programming error, the end node of one of the linked list got linked to the second list, forming an inverted Y shaped list. Wri...read more

Q60. Evaluate the Polynomial

You are given two arrays of coefficients and degrees of a polynomial expression. You need to simplify the polynomial in general form by evaluating and simplifying the expression.

For Exam...read more

Q61. Left view of binary tree

Given a binary tree. Print the Left View of the Tree.

Example :

If the input tree is as depicted in the picture: 

The Left View of the tree will be: 2 35 2 

Input format :

Elements in t...read more

Q62. Minimize Cash Flow

You are given a list of ‘transactions’ between ‘n’ number of friends. who have to give each other money. The list consists of data of receiver, sender, and transaction.

Your task is to minimiz...read more

Q63. Find the lone set bit

You are given a single non-negative integer ‘N’ who’s binary representation consists of a single ‘1’ digit and the rest of the digits are ‘0’s. Your task is to find the position of the only...read more

Q64. Nth element of modified fibbonacci series

You have been given two integers ‘X’ and ‘Y’ which are the first two integers of a series and an integer ‘N’. You have to find the Nth number of the series using the Fib...read more

Q65. Check Permutation

For a given two strings, 'str1' and 'str2', check whether they are a permutation of each other or not.

Permutations of each other

Two strings are said to be a permutation of each other when eit...read more

Q66. Spiral Order Traversal of a Binary Tree

You have been given a binary tree of 'N' nodes. Print the Spiral Order traversal of this binary tree.

For example

For the given binary tree [1, 2, 3, -1, -1, 4, 5, -1, -1,...read more

Q67. Count Squares

You are given a matrix of size N * M. Can you count the number of squares in it?

As the count will be very large, so compute it with modulo 10^9 + 7.

For Example:

Let N = 3 and M = 5 The number of ...read more

Q68. BST to sorted DLL

You are provided with a Binary Search Tree (BST), all you have to do is to convert it into the sorted doubly linked list (DLL).

For Example:

Consider the above BST, it will be converted into t...read more

Q70. Arithmetic Expression Evaluation

You are given a string ‘expression’ consists of characters ‘+’, ‘-’, ‘*’, ‘/’, ‘(‘, ‘)’ and ‘0’ to ‘9’, that represents an Arithmetic Expression in Infix Notation. Your task is t...read more

Q71. Median of two sorted arrays

You are given two sorted arrays 'A' & 'B' of sizes 'N' & 'M'. You need to find the median of the two arrays when merged. If the total number of elements i.e., N + M is even then the m...read more

Q72. Minimum Fountains

There is a one-dimensional garden of length 'N'. On each of the positions from 0 to 'N', there is a fountain, and this fountain’s water can reach up to a certain range as explained further. In ...read more

Q73. Identical Trees

You are given two binary trees with 'N' and 'M' nodes respectively. You need to return true if the two trees are identical. Otherwise, return false.

Below is the example and explanation of Identi...read more

Q74. Minimum subarray with required sum.

You have been given an array(ARR) of positive integers and an integer X. You have to find the minimum length subarray such that the sum of all of its elements is strictly grea...read more

Q75. Distinct Islands

You are given a two-dimensional array/list of integers consisting of 0s and 1s. In the list, 1 represents land and 0 represents water.

The task is to find the number of distinct islands where a ...read more

Q76. Maximum meetings

You are given the schedule of N meetings with their start time Start[i] and end time End[i]. But you have only 1 meeting room. So, you need to tell the meeting numbers you can organize in the gi...read more

Q77. System Design

You need to design a global auditorium booking platform, which could be booked from anywhere in the world. It can host multiple shows at once as it has 2 stages with different seating capacity. The...read more

Q78. Decode String

Ninja requests a PS5 from Santa on Christmas. Santa decides to give Ninja a brand new PS5, but he locks it in a safe and gives Ninja a string SECRETCODE. The password to open the safe is the length...read more

Q79. Delete Kth node from end of a linked list

You have been given a singly Linked List of 'N' nodes with integer data and an integer 'K'. Your task is to remove the Kth node from the end of the given Linked List.

Fo...read more

Q80. Reverse a Linked List.

Given a singly linked list of integers. Your task is to return the head of the reversed linked list.

For example:

The given linked list is 1 -> 2 -> 3 -> 4-> NULL. Then the reverse linked ...read more

Q82. Minimum Number of Platform Needed

You are given the arrival and departure times of N trains at a railway station in a day. You need to find the minimum of platforms required for the railway station such that no ...read more

Q83. Design Tic-Tac-Toe

Ninja has to design a 2 players game Tic-Tac-Toe played on an ‘N’ * ‘N’ grid.

Ninja has to assume the following rules while playing the game:

This game is played between two people (Player 1 a...read more

Q84. Ways To Make Coin Change

You are given an infinite supply of coins of each of denominations D = {D0, D1, D2, D3, ...... Dn-1}. You need to figure out the total number of ways W, in which you can make a change fo...read more

Q86. Euler Totient

You are given an integer 'N'. Your task is to count the number of integers between 1 and 'N' both inclusive which are coprime to 'N'.

Note:

Two numbers are coprime if their greatest common divisor(...read more

Q87. Connect Nodes at Same Level

A binary tree is a tree where each node has at most two children i.e left child and right child.

You are given a binary tree, where the structure of the node is as follow -:

class Bin...read more

Q88. Minimum Number of Platforms

You have been given two arrays, 'AT' and 'DT', representing the arrival and departure times of all trains that reach a railway station.

Your task is to find the minimum number of plat...read more

Q89. Maximum Product Subarray

You are given an array “arr'' of integers. Your task is to find the contiguous subarray within the array which has the largest product of its elements. You have to report this maximum pr...read more

Q90. Swap Number Without Temporary Variable

Given two variables ‘X’ and ‘Y’. Your task is to swap the number without using a temporary variable or third variable.

Swap means the value of ‘X’ and ‘Y’ must be interchan...read more

Q91. Longest Palindromic Subsequence

You have been given a string ‘A’ consisting of lower case English letters. Your task is to find the length of the longest palindromic subsequence in ‘A’.

A subsequence is a sequen...read more

Q92. Longest Common Prefix After Rotation

You are given two strings 'A' and 'B' where string 'A' is fixed. But you can perform left shift operations on string B any number of times.

Your task is to find out the minim...read more

Q93. Pair Sum

You are given an integer array 'ARR' of size 'N' and an integer 'S'. Your task is to return the list of all pairs of elements such that each sum of elements of each pair equals 'S'.

Note:

Each pair shou...read more

Q94. Water

You are given an array 'ARR' of positive integers, each of which represents the number of liters of water in that particular bucket, we have to make the liters of water in every bucket equal.

We are allowe...read more

Q95. Rat In A Maze

You are given a starting position for a rat which is stuck in a maze at an initial point (0, 0) (the maze can be thought of as a 2-dimensional plane). The maze would be given in the form of a squar...read more

Q97. Longest Duplicate Substring

You are given a string 'S' and you need to return the length of the longest duplicate substring in the given string. The occurrence of duplicate sub-strings can overlap also.

If there...read more