Crescendo Interview Questions and Answers

Q1. Tell me about yourself
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Q2. Why you want to join us
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Round duration - 60 Minutes
Round difficulty - Medium

The round was held on Google Meet and I was given 2 coding problems for which first I had to explain my approach and then I had to write code in Shared Google Docs and dry run on sample test cases and discuss Time and Space Complexity.

Q1. 
Validate BST Problem Statement
Given a binary tree with N nodes, determine whether the tree is a Binary Search Tree (BST). If it is a BST, return true; otherwise, return false.
A binary search tree (BST)...read more
Ans. 
Validate if a given binary tree is a Binary Search Tree (BST) or not.
• Check if the left subtree of a node contains only nodes with data less than the node's data.

• Check if the right subtree of a node contains only nodes with data greater than the node's data.

• Recursively check if both left and right subtrees are also binary search trees.
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Q2. 
Maximum Sum Path from Leaf to Root
Given a binary tree with 'N' nodes, identify the path from a leaf node to the root node that has the maximum sum among all root-to-leaf paths.
Example:
All the possibl...read more
Ans. 
Find the path from a leaf node to the root node with the maximum sum in a binary tree.
• Traverse the binary tree from leaf to root while keeping track of the sum of each path.

• Compare the sums of all paths and return the path with the maximum sum.

• Use recursion to traverse the tree efficiently and keep updating the maximum sum path.
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Round duration - 60 Minutes
Round difficulty - Medium

This was also a Data Structures and Algorithms round where I was asked to solve 2 coding problems explaining my approach with proper Complexity Analysis . After the coding questions were over there was some time left so the interviewer asked me some concepts related to DBMS.

Q1. 
Next Permutation Problem Statement
You are given a permutation of 'N' integers. A sequence of 'N' integers is considered a permutation if it includes all integers from 1 to 'N' exactly once. Your task is ...read more
Ans. 
The task is to rearrange a given permutation of 'N' integers to form the lexicographically next greater permutation.
• Iterate from right to left to find the first element that is smaller than the element to its right.

• Swap this element with the smallest element to its right that is greater than it.

• Reverse the elements to the right of the swapped element to get the lexicographically next greater permutation.
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Q2. 
Largest BST Subtree Problem Statement
You are given a binary tree with 'N' nodes. Your task is to determine the size of the largest subtree within the binary tree which is also a Binary Search Tree (BST).
...read more
Ans. 
Find the size of the largest subtree in a binary tree that is also a Binary Search 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 subtree encountered so far.

• Use recursion to solve this problem efficiently.

• Example: For the input 1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1, the largest BST subtree has a size of 3.
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Q3. Can you explain indexing in databases?
Ans. 
Indexing in databases is a technique used to improve the speed of data retrieval by creating a data structure that allows for quick lookups.
• Indexes are created on columns in a database table to speed up the retrieval of rows that match a certain condition.

• Types of indexes include B-tree, hash, and bitmap indexes.

• Indexes can improve the performance of SELECT queries but may slow down INSERT, UPDATE, and DELETE operation...read more
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Round duration - 50 Minutes
Round difficulty - Medium

This round also had 2 questions related to DS and Algo . One was from graphs and the other was an implementation of a LRU Cache . There were 2 interviewers and both of them were quite friendly and helpful. Overall, this round went well.

Q1. 
Detect Cycle in a Directed Graph
You are provided with a directed graph composed of 'N' nodes. You have a matrix called 'EDGES' with dimensions M x 2, which specifies the 'M' edges in the graph. Each edge...read more
Ans. 
Detect cycle in a directed graph using depth-first search (DFS) algorithm.
• Use DFS to traverse the graph and detect back edges (edges that point to an ancestor node).

• Maintain a visited array to keep track of visited nodes and a recursion stack to keep track of nodes in the current path.

• If a back edge is found during traversal, a cycle exists in the graph.

• Return true if a cycle is detected, false otherwise.
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Q2. 
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; otherw...read more
Ans. 
Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.
• Use a combination of hashmap and doubly linked list to efficiently implement the LRU cache.

• Keep track of the least recently used item and update it accordingly when inserting new items.

• Ensure to handle the capacity constraint by evicting the least recently used item when the cache is full.

• Implement get(...read more
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Q1. What are your salary expectations?
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Q2. Why are you looking for a change?
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Q3. Tell me about yourself.
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Q4. Share details of your previous job.
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Q1. Sale me a Pen,why should I Hire you
Ans. 
I can sell you a pen by showing you how it can solve your problems and increase your productivity.
• I understand that you need a pen to write down important information and ideas.

• This pen has a comfortable grip and writes smoothly, making it easy to use for extended periods of time.

• It also has a clip that can attach to your notebook or shirt pocket, ensuring that you always have it on hand.

• By investing in this pen, you'l...read more
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Q1. What are your salary expectations?
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Q1. Nothing to add over here
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Q2. Why didi you chose sales
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Round duration - 60 Minutes
Round difficulty - Medium

This round was purely based on Data Structures and Algorithms . One has to be fairly comfortable in solving Algorithmic problems to pass this round . Both the questions asked were quite common and luckily I had already prepared them from CodeStudio and LeetCode.

Q1. 
Binary Tree Traversals Problem Statement
Given a Binary Tree with 'N' nodes, where each node holds an integer value, your task is to compute the In-Order, Pre-Order, and Post-Order traversals of the binar...read more
Ans. 
Compute the In-Order, Pre-Order, and Post-Order traversals of a Binary Tree given in level-order format.
• Implement functions to perform In-Order, Pre-Order, and Post-Order traversals of a Binary Tree.

• Use level-order input to construct the Binary Tree.

• Traverse the Binary Tree recursively to generate the required traversals.

• Ensure proper handling of null nodes represented by -1 in the input.

• Return the three traversals as
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Q2. 
Reverse Linked List Problem Statement
Given a Singly Linked List of integers, your task is to reverse the Linked List by altering the links between the nodes.
Input:
The first line of input is an intege...read more
Ans. 
Reverse a singly linked list by altering the links between nodes.
• Iterate through the linked list and reverse the links between nodes

• Use three pointers to keep track of the current, previous, and next nodes

• Update the links between nodes to reverse the list

• Return the head of the reversed linked list
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Round duration - 45 Minutes
Round difficulty - Medium

This round basically tested some concepts from Data Structures and File Manipulation .

Q1. 
Intersection of Two Arrays Problem Statement
Given two arrays A and B with sizes N and M respectively, both sorted in non-decreasing order, determine their intersection.
The intersection of two arrays in...read more
Ans. 
The problem involves finding the intersection of two sorted arrays efficiently.
• Use two pointers to iterate through both arrays simultaneously.

• Compare elements at the pointers and move the pointers accordingly.

• Handle cases where elements are equal and update the intersection array.

• Return the intersection array as the result.
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