600+ Eben Telecom Interview Questions and Answers

Q1. Maximum Subarray Sum

Given an array of numbers, find the maximum sum of any contiguous subarray of the array.

For example, given the array [34, -50, 42, 14, -5, 86], the maximum sum would be 137, since we would ...read more

Q2. Permutation in String

You have been given two strings ‘str1’ and ‘str2’ of length N and M respectively. Your task is to check whether string ‘str2’ contains one of the permutations of string ‘str1’ as its substr...read more

Q3. Count Special Nodes in Generic Tree

Given a generic tree, find the count of all special nodes. A node is a special node if there is a path from root to that node with all distinct elements. The input was not a p...read more

Q4. Delete alternate nodes

Given a Singly Linked List of integers, delete all the alternate nodes in the list.

Example:

List: 10 -> 20 -> 30 -> 40 -> 50 -> 60 -> null Alternate nodes will be: 20, 40, and 60. Hence a...read more

Q5. Maximum sum of non-adjacent elements

You are given an array/list of ‘N’ integers. You are supposed to return the maximum sum of the subsequence with the constraint that no two elements are adjacent in the given...read more

Q7. Sum of minimum and maximum elements of all subarrays of size “K”

You are given an array consisting of N integers, and an integer, K. Your task is to determine the total sum of the minimum element and the maximum...read more

Q8. String Transformation

Given a string (STR) of length N, you have to create a new string by performing the following operation:

Take the smallest character from the first 'K' characters of STR, remove it from ST...read more

Q9. Count derangements

A Derangement is a permutation of ‘N’ elements, such that no element appears in its original position. For example, an instance of derangement of {0, 1, 2, 3} is {2, 3, 1, 0}, because 2 prese...read more

Q10. Mike and Mobile

Mike is a little boy who loves solving math problems. One day he was playing with his mom’s mobile. The mobile keypad contains 12 buttons { 10 digits(0-9) and 2 characters(‘*’ and ‘#’) }. Mike w...read more

Q11. Selling Stock

You have been given stock values/prices for N number of days. Every i-th day signifies the price of a stock on that day. Your task is to find the maximum profit which you can make by buying and sel...read more

Q12. Sort 0 1 2

You have been given an integer array/list(ARR) of size 'N'. It only contains 0s, 1s and 2s. Write a solution to sort this array/list.

Note :

Try to solve the problem in 'Single Scan'. ' Single Scan' ...read more

Q13. Detect Cycle In A Directed Graph

You are given a directed graph having ‘N’ nodes. A matrix ‘EDGES’ of size M x 2 is given which represents the ‘M’ edges such that there is an edge directed from node EDGES[i][0] ...read more

Q14. Maximum In Sliding Windows Of Size K

Given an array/list of integers of length ‘N’, there is a sliding window of size ‘K’ which moves from the beginning of the array, to the very end. You can only see the ‘K’ nu...read more

Q15. Unique Paths

You are present at point ‘A’ which is the top-left cell of an M X N matrix, your destination is point ‘B’, which is the bottom-right cell of the same matrix. Your task is to find the total number of...read more

Q16. Longest Decreasing Subsequence

You are given an array/list ARR consisting of N integers. Your task is to find the length of the longest decreasing subsequence.

A subsequence is a sequence of numbers obtained by ...read more

Q17. Longest Substring Without Repeating Characters

Given a string 'S' of length 'L', return the length of the longest substring without repeating characters.

Example:

Suppose given input is "abacb", then the length ...read more

Q18. First and Last Position of an Element In Sorted Array

You have been given a sorted array/list ARR consisting of ‘N’ elements. You are also given an integer ‘K’.

Now, your task is to find the first and last occur...read more

Q19. Trapping Rainwater

You have been given a long type array/list 'ARR' of size 'N'. It represents an elevation map wherein 'ARR[i]' denotes the elevation of the 'ith' bar. Print the total amount of rainwater that c...read more

Q20. Design a stack that supports getMin() in O(1) time and O(1) extra space

Implement a SpecialStack Data Structure that supports getMin() in O(1) time and O(1) extra space along with push(), pop(), top(), isEmpty()...read more

Q21. Strongly Connected Components (Tarjan’s Algorithm)

You are given an unweighted directed graph of 'V' vertices and 'E' edges. Your task is to print all the strongly connected components (SCCs) present in the grap...read more

Q22. Evaluation of postfix expression

An expression is called the postfix expression if the operator appears in the expression after the operands.

Example :

Infix expression: A + B * C - D Postfix expression: A B + C...read more

Q23. Number of islands

Given a boolean 2D matrix, find the number of islands. A group of connected 1s forms an island. For example, the below matrix contains 5 islands

Example:

Input : mat[][] = {{1, 1, 0, 0, 0},

{0,...read more

Q24. Minimum Path Sum

Ninjaland is a country in the shape of a 2-Dimensional grid 'GRID', with 'N' rows and 'M' columns. Each point in the grid has some cost associated with it.

Find a path from top left i.e. (0, 0) ...read more

Q25. Minimum Jumps

Bob lives with his wife in a city named Berland. Bob is a good husband, so he goes out with his wife every Friday to ‘Arcade’ mall.

‘Arcade’ is a very famous mall in Berland. It has a very unique t...read more

Q26. Weighted Job Scheduling

You are given 'N' jobs with their start time 'Start', end time 'End' and profit 'Profit'. You need to tell the maximum profit you can obtain by performing these jobs such that no two jobs...read more

Q27. Subarray With Given Sum

Given an array ARR of N integers and an integer S. The task is to find whether there exists a subarray(positive length) of the given array such that the sum of elements of the subarray eq...read more

Q28. Clone a linked List having random pointers

Given a linked list having two pointers in each node. The first one points to the next node of the list, however, the other pointer is random and can point to any node ...read more

Q29. 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

Q30. Find Row K

Given a square binary matrix ‘mat[n][n]’, find ‘K’ such that all elements in the Kth row are ‘0’ and all elements in the Kth column are ‘1’. The value of mat[k][k] can be anything (either ‘0’ or ‘1’)....read more

Q31. Find k’th character of decrypted string

Given an encoded string where repetitions of substrings are represented as substring followed by count of substrings. For example, if encrypted string is “ab2cd2” and k=4...read more

Q32. Rearrange String

You are given a string of lowercase characters. Your task is to rearrange (reorder) the string in such a way that no two adjacent characters are the same.

You have to return the rearranged strin...read more

Q33. Most Frequent Word

You are given two strings 'A' and 'B' of words. Your task is to find out the most frequent and lexicographically smallest word in string 'A', which is not present in string 'B'. If no such wor...read more

Q34. 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

Q35. Square root (decimal)

You have been given two integers 'N' and 'D', Your task is to find the square root of the number 'N' with precision up to 'D' decimal places i.e. the difference between your answer and the...read more

Q36. K Most Frequent Words

You have been given an array/list 'WORDS' of 'N' non-empty words, and an integer 'K'. Your task is to return the 'K' most frequent words sorted by their frequency from highest to lowest.

N...read more

Q37. Kth smallest element in an unsorted array

Given an unsorted array ‘arr’ of distinct integers and an integer ‘k’, your task is to find the ‘k-th’ smallest element in the array.

Example:

n = 5, k = 2 and arr[] = {...read more

Q38. 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

Q39. Merge Two Sorted Linked Lists

You are given two sorted linked lists. You have to merge them to produce a combined sorted linked list. You need to return the head of the final linked list.

Note:

The given linked ...read more

Q40. Add two number as 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 the summatio...read more

Q41. 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

Q42. Tiling Problem

Given a “2 x n” board and tiles of size “2 x 1”, count the number of ways to tile the given board using the 2 x 1 tiles. A tile can either be placed horizontally i.e., as a 1 x 2 tile or verticall...read more

Q43. Largest rectangle in a histogram

You have been given an array/list 'HEIGHTS' of length ‘N. 'HEIGHTS' represents the histogram and each element of 'HEIGHTS' represents the height of the histogram bar. Consider th...read more

Q44. Loot Houses

A thief wants to loot houses. He knows the amount of money in each house. He cannot loot two consecutive houses. Find the maximum amount of money he can loot.

Input Format :

The first line of input c...read more

Q45. Given a string, find the next smallest palindrome

You are given a number 'N' in the form of a string 'S', your task is to find the smallest number strictly greater than the given number 'N' which is a palindrome...read more

Q46. Minimum number of swaps required to sort an array

You have been given an array 'ARR' of 'N' distinct elements.

Your task is to find the minimum no. of swaps required to sort the array.

For example:

For the given...read more

Q47. K Closest Points To Origin

Your house is located at the origin of a 2-D plane. You have 'N' neighbours who live at 'N' different points on the plane. You want to visit exactly 'K' different neighbours who live c...read more

Q48. Reverse DLL nodes in groups

You are given a Doubly Linked List of integers and a positive integer 'K' representing the group size. Modify the linked list by reversing every group of 'K' nodes in the linked list....read more

Q49. Duplicate In Array

You are given an array ‘ARR’ of size ‘N’ containing each number between 1 and ‘N’ - 1 at least once. There is a single integer value that is present in the array twice. Your task is to find th...read more

Q50. Maximum Subtree Sum

You are given an arbitrary binary tree consisting of N nodes. Your task is to find the largest subtree sum.

Note :

1. The value of any node will not be equal to zero. 2. Subtree of a node X i...read more

Q51. Intersection of Linked List

You are given two Singly Linked List of integers, which are merging at some node of a third linked list.

Your task is to find the data of the node at which merging starts. If there is...read more

Q52. BST iterator

You are given a class named as BSTIterator that represents an iterator over inorder traversal of a binary search tree. You need to implement the following things as follows:

1. BSTIterator(Node root...read more

Q53. Merge two sorted linked list

You are given two sorted linked lists. You have to merge them to produce a combined sorted linked list. You need to return the head of the final linked list.

Note:

The given linked ...read more

Q54. All Prime Numbers less than or equal to N

You are given a positive integer 'N'. Your task is to return all the prime numbers less than or equal to the 'N'.

Note:

1) A prime number is a number that has only two f...read more

Q55. Fish Eater

There is a river which flows in one direction. One day, the river has 'N' number of fishes. You are given an array 'FISHES' of integers representing the size of 'N' fishes. The fishes are present in t...read more

Q56. Is Binary Heap Tree

You have been given a binary tree of integers.

Your task is to check if it is a binary heap tree or not.

Note:

A binary tree is a tree in which each parent node has at most two children. A bi...read more

Q57. 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

Q58. Loot House

There are n houses build in a line, each of which contains some value in it. A thief is going to steal the maximal value of these houses, but he can’t steal in two adjacent houses because the owner of...read more

Q59. Print Nodes at Distance K From a Given Node

You are given an arbitrary binary tree, a node of the tree, and an integer 'K'. You need to find all such nodes which have a distance K from the given node and return ...read more

Q60. Find Missing Number In String

You had a sequence of consecutive nonnegative integers. You appended all integers at the end of each other to form a string ‘S’ without any separators. While appending each integer ...read more

Q61. Ninja and BInary String

Ninja is given a binary string ‘S’ of size ‘N’ by his friend, the task is to check if the binary string ‘S’ can be sorted in decreasing order by removing any number of the non-adjacent ch...read more

Q62. Missing Numbers

You are given an array 'ARR' of distinct positive integers. You need to find all numbers that are in the range of the elements of the array, but not in the array. The missing elements should be p...read more

Q63. Optimize Memory Usage

Alex has a computer with ‘K’ memory spaces. He has a list of ‘N’ different document downloads that he would like to do, each of which consumes some unique memory usage. He also has ‘M’ comp...read more

Q64. Flatten a linked List

You are given a linked list containing N nodes, where every node in the linked list contains two pointers, first one is ‘NEXT’ which points to the next node in the list and the second one i...read more

Q65. Family Structure

Aakash is a member of Ninja club. He has a weird family structure. Every male member (M) gives birth to a male child first and then a female child, whereas every female (F) member gives birth to...read more

Q66. Ninja and power of 2

Ninja loves playing with numbers. So one day, he wants to arrange a few numbers in the ‘N’ number of rows. The first row contains 1 number, the second row has two numbers, the third row has ...read more

Q67. LCA Of Binary Tree

You have been given a Binary Tree of distinct integers and two nodes ‘X’ and ‘Y’. You are supposed to return the LCA (Lowest Common Ancestor) of ‘X’ and ‘Y’.

The LCA of ‘X’ and ‘Y’ in the bina...read more

Q68. Compress the String

Write a program to do basic string compression. For a character which is consecutively repeated more than once, replace consecutive duplicate occurrences with the count of repetitions.

Exampl...read more

Q69. STRING KA KHEL

Ninja started a gaming shop and for that shop, he is planning to make a new game ‘String Ka Khel’. In that game user is provided with ‘N’ number of strings and he has to find out the maximum lengt...read more

Q70. Construct tree from Preorder Traversal

Given an array ‘pre[]’ of ‘n’ elements that represent Preorder traversal of a spacial binary tree where every node has either 0 or 2 children. Also Given a boolean array ‘i...read more

Q71. Palindrome Partitioning

You are given a string 'S'. Your task is to partition 'S' such that every substring of the partition is a palindrome. You need to return all possible palindrome partitioning of 'S'.

Note:...read more

Q72. Longest Increasing Subsequence

'N' students are standing in a row. You are given the height of every student standing in the row. Your task is to find the longest strictly increasing subsequence of heights from ...read more

Q73. Maximum element between two nodes of BST

Given a Binary Search Tree and two integers NODE1 and NODE2. You have to find the maximum element in the path from NODE1 to NODE2.

A binary search tree (BST), also called...read more

Q74. Maximum Subarray Sum

You are given an array/list ARR consisting of N integers. Your task is to find the maximum possible sum of a non-empty subarray(contagious) of this array.

Note: An array C is a subarray of a...read more

Q75. Next Greater Number

You are given a string S which represents a number. You have to find the smallest number strictly greater than the given number which contains the same set of digits as of the original number...read more

Q76. Sum Between Zeros

You are given a Singly Linked List which contains a series of integers separated by ‘0’.

Between two zeroes, you have to merge all the nodes lying between them into a single node which contains ...read more

Q77. Ninja and Binary Tree

Ninja has to implement a binary tree class from scratch. The Ninja can perform three types of queries on this binary tree.

• ‘I’ ‘VAL’: In this query, Ninja has to insert a Node with the val...read more

Q78. Mean Median Mode

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 array.

2. Median -...read more

Q79. Zig - Zag Array

You are given an array of distinct elements, and you have to rearrange the array elements in a zig-zag fashion. In other words, for every odd position ‘i’ in the array 'ARR,' 'ARR'[i] should be g...read more

Q80. Pair sum in a BST

You are given a binary search tree and an integer ‘S’. Your task is to find all the pairs of nodes in the BST which sum to the value ‘S’. If no such pair exists, then print -1 - 1.

Note:

You ca...read more

Q81. Peer to peer network dicussion

Given a peer to peer network, how will you design an algorithm to transfer data from one to node to the other receiver nodes? In its simplest form, a peer-to-peer (P2P) network is ...read more

Q83. 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

Q84. Merge Two Sorted Linked Lists

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...read more

Q85. Longest Common Subsequence

You have been given two Strings “STR1” and “STR2” of characters. Your task is to find the length of the longest common subsequence.

A String ‘a’ is a subsequence of a String ‘b’ if ‘a’...read more

Q86. Find Pair With Smallest Difference

Given two unsorted arrays of non-negative integers, 'arr1' and 'arr2' of size 'N' and 'M', respectively. Your task is to find the pair of elements (one from each array), such t...read more

Q87. Max element in the path

Given a Binary Search Tree and two integers NODE1 and NODE2. You have to find the maximum element in the path from NODE1 to NODE2.

A binary search tree (BST), also called an ordered or so...read more

Q88. Edit Distance

You are given two strings 'S' and 'T' of lengths 'N' and 'M' respectively. Find the "Edit Distance" between the strings.

Edit Distance of two strings is the minimum number of steps required to make...read more

Q89. Maximum In Subarray

Given an array and an integer K, find the maximum for each and every contiguous subarray of size k.

Examples :

Input: arr[] = {1, 2, 3, 1, 4, 5, 2, 3, 6}, K = 3

Output: 3 3 4 5 5 5 6

Explanation...read more

Q90. Longest Increasing Subsequence

For a given array with N elements, you need to find the length of the longest subsequence from the array such that all the elements of the subsequence are sorted in strictly increa...read more

Q91. AWS Trucks

The problem statement involved the use of amazon trucks which had to deliver system requirements across an AWS region which contains N office buildings. The various location of buildings are given in ...read more

Q92. Circular Move

Given a sequence of moves for a robot, check if the sequence is circular or not. A sequence of moves is circular if first and last positions of robot are same. A move can be on of the following.

G...read more

Q93. Kth Smallest and Largest Element of Array

You are given an array ‘Arr’ consisting of ‘N’ distinct integers and a positive integer ‘K’. Find out Kth smallest and Kth largest element of the array. It is guaranteed...read more

Q94. Aptitude Question

You pull out 2 balls, one after another, from a bag which has 20 blue and 13 red balls in total. If the balls are of similar colour, then the balls are replaced with a blue ball, however, if th...read more

Q95. Check whether K is present or not

The second question was a mixture of OOP and Problem Solving. You are provided with a function that has two parameters Object of a class LIST and an integer 'k.' The LIST class...read more

Q96. Next Greater Element

For a given array/list of integers of size N, print the Next Greater Element(NGE) for every element. The Next Greater Element for an element X is the first element on the right side of X in ...read more

Q97. 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

Q98. Minimum number of swaps

You are given a string ‘S’ of length ‘N’, an array A of length ‘M’ ( consisting of lowercase letters). and a positive integer ‘K’. You can take a character from 'A' and change any charac...read more

Q99. Print all possible paths from top left corner to bottom right corner of a 2-D matrix

You are given an ‘M*N’ Matrix, You need to print all possible paths from its top left corner to the bottom right corner if giv...read more