MindSquare Technologies Interview Questions and Answers

Round duration - 180 min
Round difficulty - Hard

Q1. 
Longest Common Subsequence Problem Statement
Given two strings STR1 and STR2, determine the length of their longest common subsequence.
A subsequence is a sequence that can be derived from another sequen...read more
Ans. 
The problem involves finding the length of the longest common subsequence between two given strings.
• Use dynamic programming to solve the problem efficiently.

• Create a 2D array to store the lengths of common subsequences of substrings.

• Iterate through the strings to fill the array and find the length of the longest common subsequence.

• Example: For input STR1 = 'abcde' and STR2 = 'ace', the longest common subsequence is 'ac
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Q2. 
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...read more
Ans. 
Yes, the 0/1 Knapsack problem can be solved using dynamic programming with a space complexity of not more than O(W).
• Use a 1D array to store the maximum value that can be stolen for each weight capacity from 0 to W.

• Iterate through each item and update the array based on whether including the item would increase the total value.

• The final value in the array at index W will be the maximum value that can be stolen.
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Q3. 
K Largest Elements Problem Statement
You are given an unsorted array containing 'N' integers. Your task is to find the 'K' largest elements from this array and return them in non-decreasing order.
Input:
T...read more
Ans. 
Yes, the problem can be solved in less than O(N*log(N)) time complexity using the Quick Select algorithm.
• Implement Quick Select algorithm to find the Kth largest element in O(N) time complexity.

• Partition the array around a pivot element and recursively search in the left or right partition based on the position of the pivot.

• Once you find the Kth largest element, return all elements greater than or equal to it in non-de
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Round duration - 60 Minutes
Round difficulty - Medium

Q1. 
Size of Largest BST in a Binary Tree
Given a binary tree with 'N' nodes, determine the size of the largest subtree that is also a Binary Search Tree (BST).
Explanation:
A Binary Search Tree (BST) is def...read more
Ans. 
Find the size of the largest BST subtree in a binary tree.
• Traverse the tree in a bottom-up manner to check if each subtree is a BST.

• Keep track of the size of the largest BST found so far.

• Recursively check if the current subtree is a BST and update the size accordingly.
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Q2. 
Matrix Chain Multiplication Problem
Given 'N' 2-dimensional matrices and an array ARR of length N + 1, where the first N integers denote the number of rows in each matrix and the last integer represents t...read more
Ans. 
Find the minimum number of multiplication operations required to multiply a series of matrices together.
• Use dynamic programming to solve this problem efficiently.

• Create a 2D array to store the minimum number of operations needed to multiply matrices.

• Iterate through different combinations of matrices to find the optimal solution.

• Consider the dimensions of the matrices to determine the number of operations required.

• Calcu...read more
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Q3. 
Rotate Linked List Problem Statement
Given a linked list consisting of 'N' nodes and an integer 'K', your task is to rotate the linked list by 'K' positions in a clockwise direction.
Example:
Input:
Li...read more
Ans. 
Rotate a linked list by K positions in a clockwise direction.
• Traverse the linked list to find the length and the last node.

• Connect the last node to the head to form a circular linked list.

• Find the new head by moving (length - K) steps from the last node.

• Break the circular list at the new head to get the rotated linked list.
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Round duration - 45 minutes
Round difficulty - Easy

Q1. 
Longest Palindromic Substring Problem Statement
You are provided with a string STR of length N. The task is to find the longest palindromic substring within STR. If there are several palindromic substring...read more
Ans. 
Given a string, find the longest palindromic substring within it.
• Iterate through the string and expand around each character to find palindromes

• Keep track of the longest palindrome found so far

• Return the longest palindromic substring
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Q1. IT WAS MCQ CODING OUTPUT BASED ROUND IN WHICH TOTAL 45 QUESTION
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Q1. IT WAS SUBJECTIVE CODING ROUND IN WHICH 1 OUTPUT BASED AND 3 CODING ROUND
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IT WAS 3RD CODING ROUND IN WHICH 3 CODING QUESTIONS AND DURATION 75MIN

Round duration - 90 minutes
Round difficulty - Easy

It was just after the first round in the morning

Q1. 
Huffman Coding Challenge
Given an array ARR of integers containing 'N' elements where each element denotes the frequency of a character in a message composed of 'N' alphabets of an alien language, your ta...read more
Ans. 
Implement a function to generate Huffman codes for characters based on their frequencies in an alien language message.
• Use a priority queue to build the Huffman tree efficiently.

• Assign '0' and '1' to left and right branches of the tree respectively to generate unique binary codes.

• Ensure that each code distinctly identifies its corresponding character and minimizes the total number of bits used for the message.
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Round duration - 90 Minutes
Round difficulty - Medium

1 hr after the second round got over and results were announced in the morning.

Q1. 
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...read more
Ans. 
The task is to find the total number of ways to make change for a specified value using given denominations.
• Create a dynamic programming table to store the number of ways to make change for each value up to the target value.

• Iterate through each denomination and update the table accordingly based on the current denomination.

• The final answer will be the value in the table at the target value.

• Consider edge cases such as w...read more
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Round duration - 90 Minutes
Round difficulty - Medium

10 A.M in the morning.
The interviewers were very knowledgeable and humble

Q1. 
Unique Element In Sorted Array
Nobita wants to impress Shizuka by correctly guessing her lucky number. Shizuka provides a sorted list where every number appears twice, except for her lucky number, which a...read more
Ans. 
Find the unique element in a sorted array where all other elements appear twice.
• Iterate through the array and XOR all elements to find the unique element.

• Use a hash set to keep track of elements and find the unique one.

• Sort the array and check adjacent elements to find the unique one.
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Q2. 
Find Nodes at Distance K in a Binary Tree
Your task is to find all nodes that are exactly a distance K from a given node in an arbitrary binary tree. The distance is defined as the number of edges between ...read more
Ans. 
Find all nodes at distance K from a given node in a binary tree.
• Perform a depth-first search starting from the target node to find nodes at distance K.

• Use a recursive function to traverse the tree and keep track of the distance from the target node.

• Maintain a set to store visited nodes and avoid revisiting them.

• Return the list of nodes found at distance K from the target node.

• Example: For the given input tree, target n...read more
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Round duration - 90 Minutes
Round difficulty - Medium

It was after the first technical interview round.
Got a mail for the second interview round .
Timings approx 12 AM

Q1. 
Remove BST Keys Outside Given Range
Given a Binary Search Tree (BST) and a specified range [min, max], your task is to remove all keys from the BST that fall outside this range. The BST should remain vali...read more
Ans. 
Remove keys outside given range from a Binary Search Tree while keeping it valid.
• Traverse the BST in inorder and remove nodes outside the specified range

• Recursively check left and right subtrees for nodes to remove

• Update pointers to maintain the validity of the BST

• Return the inorder traversal of the adjusted BST
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Q2. 
Inorder Successor in a Binary Tree
Given an arbitrary binary tree and a specific node within that tree, determine the inorder successor of this node.
Explanation:
The inorder successor of a node in a bi...read more
Ans. 
Given a binary tree and a specific node, find its inorder successor in the tree.
• Perform an inorder traversal of the binary tree to find the successor node.

• If the given node has a right child, the successor is the leftmost node in the right subtree.

• If the given node does not have a right child, backtrack to find the ancestor whose left child is the given node.
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Round duration - 30 Minutes
Round difficulty - Easy

Got a call from Hr after clearance of the first 2 rounds.
Timing were 5:30 P.M

Round duration - 60 minutes
Round difficulty - Medium

Students who qualified in first round gets link for this round, this round had 4 questions in total, out of which 1 was output based and 3 was DSA based.

Q1. 
Validate Binary Tree Nodes Problem
You are provided with 'N' binary tree nodes labeled from 0 to N-1, where node i has two potential children, recorded in the LEFT_CHILD[i] and RIGHT_CHILD[i] arrays. Dete...read more
Ans. 
The task is to determine if the given binary tree nodes form exactly one valid binary tree.
• Check if there is only one root node (a node with no parent)

• Check if each node has at most one parent

• Check if there are no cycles in the tree

• Check if all nodes are connected and form a single tree
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Round duration - 75 minutes
Round difficulty - Medium

This round was of 70-75 minutes and had 3 coding questions of easy to medium level. There was some restrictions like we cannot use built-in functions in both second and third subjective round.

Q1. 
Balanced Binary Trees Problem Statement
You are provided with an integer 'H'. Your task is to determine and print the maximum number of balanced binary trees possible with height 'H'.
A balanced binary t...read more
Ans. 
The maximum number of balanced binary trees possible with a given height is to be counted and printed.
• A balanced binary tree is one in which the difference between the left and right subtree heights is less than or equal to 1.

• The number of balanced binary trees can be calculated using dynamic programming.

• The number of balanced binary trees with height 'H' can be obtained by summing the product of the number of balanced...read more
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Round duration - 60 minutes
Round difficulty - Medium

This was face to face interview round of 60 minutes. It was mostly based on DSA, some questions was also asked related to my projects and DBMS. Interviewer was kind and good.

Q1. 
Wave Array Sorting Problem
Your goal is to sort a given unsorted array ARR such that it forms a wave array.
Explanation:
After sorting, the array should satisfy the wave pattern conditions:
• ARR[0] &...read more
Ans. 
The task is to sort an array in a wave form, where each element is greater than or equal to its adjacent elements.
• Iterate through the array and swap adjacent elements if they do not follow the wave pattern

• Start from the second element and compare it with the previous element, swap if necessary

• Continue this process until the end of the array

• Repeat the process for the remaining elements

• Return the sorted wave array
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Q2. 
Maximum Sum BST Problem Statement
You are presented with a Binary Tree 'root', which may not necessarily be a Binary Search Tree (BST). Your objective is to identify the maximum sum of node values in any ...read more
Ans. 
The task is to find the maximum sum of node values of any subtree that is a Binary Search Tree(BST).
• Traverse the binary tree in a bottom-up manner

• For each node, check if it forms a BST and calculate the sum of its subtree

• Keep track of the maximum sum encountered so far

• Return the maximum sum
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Round duration - 135 minutes
Round difficulty - Hard

This was the final technical round, it was around 2.5 hours long and based on mostly DSA and little bit Projects, DBMS, OS. Josh mainly focus on DSA and on Tree Data Structure in interview.

Q1. 
Pair Sum in BST Problem Statement
Given a Binary Search Tree (BST) and a target value K, determine if there exist two unique elements in the BST such that their sum equals K.
Input:
An integer T, the nu...read more
Ans. 
The task is to check if there exist two unique elements in the given BST such that their sum is equal to the given target 'K'.
• Traverse the BST in-order and store the elements in a sorted array

• Use two pointers, one at the beginning and one at the end of the array

• Check if the sum of the elements at the two pointers is equal to the target 'K'

• If the sum is less than 'K', move the left pointer to the right

• If the sum is grea...read more
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Q2. 
Find Nodes at Distance K in a Binary Tree
Your task is to find all nodes that are exactly a distance K from a given node in an arbitrary binary tree. The distance is defined as the number of edges between ...read more
Ans. 
The task is to find all nodes in a binary tree that are at a distance K from a given node.
• Implement a function that takes the binary tree, target node, and distance K as input.

• Use a depth-first search (DFS) algorithm to traverse the tree and find the nodes at distance K.

• Keep track of the distance from the current node to the target node while traversing.

• When the distance equals K, add the current node to the result lis...read more
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Round duration - 20 minutes
Round difficulty - Easy

This was the simple 20 minutes round