Ola Cabs Software Development Engineer Interview Questions and Answers

Find the subset of an array with the largest sum of continuous positive numbers.

• Iterate through the array and keep track of the current sum and the maximum sum seen so far.

• If the current element is positive, add it to the current sum. If it is negative, reset the current sum to 0.

• Also keep track of the start and end indices of the maximum sum subset.

• Return the subset using the start and end indices.

Find smallest substring in s1 containing all characters of s2.

• Create a hash table of characters in s2

• Use sliding window technique to find smallest substring in s1

• Check if all characters in s2 are present in the substring

• Update the smallest substring if a smaller one is found

Algorithm to reverse a linked list

• Create a new empty linked list

• Traverse the original linked list and insert each node at the beginning of the new list

• Return the new list

Lazy loading is a technique used to defer the loading of non-critical resources until they are needed.

• Advantages: faster initial page load, reduced bandwidth usage, improved user experience

• Disadvantages: increased complexity, potential for slower subsequent page loads, difficulty with SEO

• Examples: images, videos, and other media files can be loaded only when they are visible on the screen

Ajax is a technique for creating fast and dynamic web pages. AngularJS is a framework for building dynamic web applications, while jQuery is a library for simplifying HTML DOM traversal and manipulation.

• Ajax stands for Asynchronous JavaScript and XML

• It allows web pages to be updated asynchronously by exchanging data with a web server behind the scenes

• AngularJS is a JavaScript framework that extends HTML with new attrib...read more

A traffic light system controls the flow of traffic at intersections.

• The system consists of three lights: red, yellow, and green.

• Each light has a specific duration for which it stays on.

• The system also includes sensors to detect the presence of vehicles and pedestrians.

• The duration of each light can be adjusted based on traffic patterns.

• The system can be connected to a central control system for remote monitoring and m

Given a 2D matrix with doors and walls, fill distance matrix with minimum distance to the nearest door.

• Iterate through the matrix and find the doors

• Use Breadth-First Search (BFS) to calculate the minimum distance from each cell to the nearest door

• Update the distance matrix with the minimum distances

Find kth smallest element in unordered array with O(1) space

• Use the QuickSelect algorithm to partition the array and find the kth smallest element

• Choose a pivot element and partition the array into two subarrays

• Recursively partition the subarray that contains the kth smallest element

• Repeat until the pivot element is the kth smallest element

• Time complexity: O(n) average case, O(n^2) worst case

To find friends of friends who are not already friends with you, we can first find your friends and then their friends excluding yourself and your friends.

• Get your list of friends

• For each friend, get their list of friends

• Exclude yourself and your friends from the final list of friends of friends

Implementing a shuffle function for a playlist of songs

• Create a new empty playlist

• Randomly select a song from the original playlist and add it to the new playlist

• Remove the selected song from the original playlist

• Repeat until all songs have been added to the new playlist

• Return the new shuffled playlist

Memory leak is a situation where a program fails to release memory it no longer needs.

• Memory leaks can cause a program to consume more and more memory over time, eventually leading to crashes or other issues.

• Memory leaks can be caused by programming errors such as not freeing memory after it is no longer needed.

• Tools like valgrind can be used to detect memory leaks in C and C++ programs.

• Examples of memory leaks include...read more

Arrays have fixed size and can lead to memory wastage and performance issues.

• Arrays have a fixed size and cannot be resized dynamically.

• Inserting or deleting elements in an array can be time-consuming.

• Arrays can lead to memory wastage if they are not fully utilized.

• Arrays can cause performance issues if they are too large and need to be traversed frequently.

• Arrays can also be prone to buffer overflow attacks.

• Example: A...read more

Function to hide text on mouse click in JavaScript

• Create a function that takes an element as input

• Add an event listener to the element for a mouse click

• Toggle the element's display property between 'none' and its original value

Find two elements in an unsorted array whose sum is equal to a given number x.

• Use a hash table to store the difference between x and each element in the array.

• Iterate through the array and check if the current element is in the hash table.

• Return the pair of elements that add up to x.

BST stands for Binary Search Tree, a data structure used for efficient searching and sorting operations.

• BST is a tree-like data structure where each node has at most two children.

• The left child of a node contains a value less than the parent node, while the right child contains a value greater than the parent node.

• BST allows for efficient searching and sorting operations with a time complexity of O(log n).

• Examples of a...read more

Number of possible BSTs with 2 and 3 nodes.

• For 2 nodes, only 2 BSTs are possible.

• For 3 nodes, 5 BSTs are possible.

• Number of BSTs can be calculated using Catalan numbers formula.

• Catalan(2) = 2, Catalan(3) = 5.

Answering the question about possible trees with two and three nodes.

• For two nodes, there is only one possible tree.

• For three nodes, there are three possible trees.

• The formula for calculating the number of possible trees with n nodes is (2n-3)!!.

• The double exclamation mark represents the double factorial function.

• The double factorial function is defined as n!! = n(n-2)(n-4)...(1 or 2).

B+ trees are balanced trees used for indexing and searching large amounts of data.

• B+ trees are similar to binary search trees but have multiple keys per node.

• They are commonly used in databases and file systems.

• B+ trees have a high fanout, reducing the number of disk accesses required for searching.

• They are also self-balancing, ensuring efficient performance even with large amounts of data.

• Example: In a database, a B+ ...read more

Yes, I have a few questions.

• Can you tell me more about the team I'll be working with?

• What is the company culture like?

• What are the biggest challenges the team is currently facing?

• Can you walk me through the development process for a typical project?

• What opportunities are there for professional growth and development?

I prefer hash tables for their constant time lookup and insertion.

• Hash tables are efficient for storing and retrieving data.

• They have constant time complexity for both insertion and lookup.

• They can be implemented using arrays or linked lists.

• Examples include Python's dictionary and Java's HashMap.

Yes, we can implement a stack using two queues.

• Push operation: Enqueue the element to the first queue.

• Pop operation: Dequeue all elements from the first queue and enqueue them to the second queue until the last element. Dequeue and return the last element. Swap the names of the queues.

• Top operation: Same as pop operation but don't dequeue the last element.

• Example: Push 1, 2, 3. Queue 1: 1 2 3. Queue 2: empty. Pop opera...read more

Find minimum no of platforms required to avoid collision between trains based on their arrival and departure times.

• Sort both arrays in ascending order

• Initialize platform count and max count to 1

• Loop through both arrays and compare arrival and departure times

• If arrival time is less than or equal to departure time, increment platform count

• Else, decrement platform count

• Update max count if platform count is greater than ma

JVM stands for Java Virtual Machine. It is an abstract machine that provides a runtime environment for Java programs.

• JVM is responsible for interpreting the compiled Java code and executing it.

• It provides platform independence by converting bytecode into machine-specific code.

• JVM has various components like class loader, bytecode verifier, and execution engine.

• Compiler converts source code into bytecode, while JVM exec...read more

I am a software engineer with experience in developing web applications and a passion for learning new technologies.

• Experienced in developing web applications using technologies such as Java, Spring, and Angular

• Passionate about learning new technologies and keeping up with industry trends

• Strong problem-solving skills and ability to work in a team environment

• Completed a Bachelor's degree in Computer Science from XYZ Uni

PayTM is an Indian e-commerce payment system and digital wallet company.

• PayTM was founded in 2010 by Vijay Shekhar Sharma.

• It started as a mobile recharge and bill payment platform.

• PayTM has expanded to offer services like online shopping, movie ticket booking, and travel bookings.

• It also offers a digital wallet that can be used to pay for various services and products.

• PayTM has over 350 million registered users and is ...read more

I would like to add a feature for splitting bills among friends.

• The feature would allow users to split bills for movies, dinners, etc.

• Users can select friends from their contact list and split the bill equally or unequally.

• The app would send a notification to the selected friends to pay their share.

• The feature would make it easier for users to split expenses and avoid awkward conversations.

• It would also encourage more

My favourite app is Spotify. I would like to see improvements in the algorithm for personalized playlists.

• Improved algorithm for personalized playlists

• Better integration with social media platforms

• Option to create collaborative playlists with friends

My favourite subject is Computer Science.

• I enjoy programming and problem-solving.

• I find algorithms and data structures fascinating.

• I am interested in artificial intelligence and machine learning.

• I like learning about new technologies and keeping up with industry trends.

I choose NIT Hamirpur because of its excellent academic reputation and beautiful campus.

• NIT Hamirpur has a strong focus on academics and research, which aligns with my career goals.

• The campus is located in a serene and picturesque location, which provides a conducive environment for learning.

• The faculty members are highly experienced and knowledgeable, and are always willing to help students.

• The college has state-of-th...read more

Find the odd repeating element from an array of strings

• Use a hash table to count the frequency of each element

• Iterate through the hash table to find the element with an odd count

Finding an element in a sorted 2D matrix

• Start from the top right corner or bottom left corner

• Compare the target element with the current element

• Move left or down if the target is smaller, else move right or up

• Repeat until the target is found or all elements are checked

SQL query to find Nth highest salary from table

• Use ORDER BY and LIMIT clauses

• Use subquery to get the Nth highest salary

• Handle cases where there are less than N distinct salaries

Function to swap '3' and '4' without using if-else

• Use XOR operator to swap the values

• Convert the input to ASCII code and perform the swap

• Use a lookup table to map the values

I am a software developer with experience in Java and Python.

• Proficient in Java and Python programming languages

• Experience in developing web applications using Spring framework

• Familiarity with database management systems like MySQL and MongoDB

PAYTM is a leading digital payment platform in India with a wide range of services.

• PAYTM has a user-friendly interface and offers a seamless payment experience.

• It provides a variety of services like mobile recharges, bill payments, and online shopping.

• PAYTM has a strong focus on security and fraud prevention measures.

• It has a large user base and is widely accepted by merchants across India.

• PAYTM is constantly innovatin...read more

Yes, I am open to pursuing further studies in the future.

• I believe in continuous learning and staying updated with the latest technologies.

• Further studies can help me specialize in a particular field and enhance my skills.

• I may consider pursuing a master's degree in computer science or a related field.

• However, my immediate focus is on gaining practical experience and contributing to the organization.

PAYTM grew fast due to its innovative approach and early adoption of digital payments.

• Early adoption of digital payments in India

• Innovative approach with features like mobile recharges, bill payments, and cashback offers

• Expansion into e-commerce and financial services

• Strategic partnerships with major companies like Uber and Alibaba