Ola Cabs Software Engineer Interview Questions and Answers

Reverse a linked list

• Iteratively swap the next and previous pointers of each node

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

• Update the head pointer to the last node after reversing

I appreciate the company's commitment to innovation and employee development.

• Strong focus on innovation in software development

• Opportunities for professional growth and development

• Positive company culture and work environment

I am impressed by the company's innovative projects and collaborative work environment.

• Impressed by innovative projects

• Desire to work in a collaborative environment

• Excited about potential for growth and learning opportunities

Normalization organizes data to reduce redundancy and improve integrity in databases.

• Identify functional dependencies: Determine which attributes depend on others.

• First Normal Form (1NF): Ensure all entries in a column are atomic. E.g., split 'Phone Numbers' into separate entries.

• Second Normal Form (2NF): Remove partial dependencies. E.g., if 'StudentID' determines 'StudentName', separate into a new table.

• Third Normal ...read more

Understanding join and groupby queries is essential for data manipulation in SQL databases.

• JOIN combines rows from two or more tables based on a related column. Example: SELECT * FROM A JOIN B ON A.id = B.a_id;

• INNER JOIN returns records with matching values in both tables. Example: SELECT * FROM A INNER JOIN B ON A.id = B.a_id;

• LEFT JOIN returns all records from the left table and matched records from the right table. E...read more

Web server handles HTTP requests and responses, while application server executes application logic.

• Web server serves static content like HTML, CSS, JS files

• Application server executes dynamic code like Java, Python, Ruby

• Web server communicates with client, application server communicates with database

• Examples of web servers: Apache, Nginx, IIS

• Examples of application servers: Tomcat, JBoss, WebSphere

This question involves coding a pattern based on specified rules, typically using loops and conditionals.

• Identify the pattern structure (e.g., stars, numbers).

• Use nested loops for rows and columns.

• Example: For n=3, output could be: * ** ***

• Consider edge cases like n=0 or negative values.

Find sum of k smallest numbers in a BST.

• Traverse the BST in-order and add the k smallest numbers to a sum variable.

• Use a priority queue to keep track of the k smallest numbers.

• If k is greater than the number of nodes in the BST, return the sum of all nodes.

• If k is 0, return 0.

Design algorithm and database for seat booking system of BookMyShow and handle failed payments.

• Create a database with tables for movies, theaters, seats, bookings, and payments

• Use a locking mechanism to prevent double booking of seats

• If payment fails, release the locked seats and notify the user

• Write a query to get the timestamp in SQL: SELECT CURRENT_TIMESTAMP;

Code for time stamp in C

• Use the time.h header file

• Call the time() function to get the current time in seconds

• Convert the time to a string using strftime() function

• Use the format string to specify the desired format of the time stamp

Rearrange array in consecutive pair multiplication in descending order.

• Create a new array to store the multiplied values

• Use a loop to iterate through the original array and multiply consecutive pairs

• Write a compare function to sort the new array in descending order

Code to rearrange an array in maximum-minimum form.

• Sort the array in descending order.

• Create a new array and alternate between adding the maximum and minimum values from the sorted array.

• Return the new array.

• Time complexity: O(nlogn)

• Space complexity: O(n)

stoi() function converts a string to an integer.

• stoi() is a C++ function that takes a string as input and returns an integer.

• It is used to convert a string of digits into an integer.

• It can also handle negative numbers and ignore leading whitespace.

• Example: int num = stoi("123"); // num is now 123

Code for finding the longest common substring in an array of strings.

• Iterate through the first string and check for all possible substrings

• Check if the substring is present in all other strings

• Keep track of the longest common substring found so far

• Return the longest common substring

Answers to common technical questions in a software engineering interview

• A transaction in DBMS is a sequence of operations that must be treated as a single unit of work. ACID properties ensure reliability and consistency of transactions.

• A thread is a lightweight process that shares memory and resources with other threads in the same process. A process is a separate instance of a program.

• Common Linux commands include ls...read more

Sorts an array of strings in ascending order.

• Use a sorting algorithm like bubble sort, selection sort, or merge sort.

• Compare adjacent elements and swap them if they are in the wrong order.

• Repeat the process until the array is sorted.