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Ola Cabs Software Developer Interview Questions and Answers
10 Interview questions
Minimum Number Of Taps To Water Garden Problem Statement
You are required to determine the minimum number of taps that need to be opened to water an entire one-dimensional garden defined along the x-axis, ...
Find the minimum number of taps to water an entire garden along the x-axis.
Iterate over the taps and find the farthest point each tap can reach.
Sort the taps based on their starting points and use a greedy approach to select the taps.
Keep track of the farthest point reachable by the selected taps and the number of taps opened.
Return the minimum number of taps needed to water the entire garden or -1 if it's impossi...
Count Leaf Nodes in a Binary Tree
Given a binary tree, your task is to count and return the number of leaf nodes present in it.
A binary tree is a data structure where each node has at most two children, ...
Count and return the number of leaf nodes in a binary tree.
Traverse the binary tree and count nodes with both left and right children as NULL.
Use recursion to traverse the tree efficiently.
Leaf nodes have no children, so check for NULL left and right children to identify them.
Diagonal Traversal of a Binary Tree Problem Statement
Given a binary tree, your task is to determine the diagonal traversal of the tree.
Example:
Input:
1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1
Output:
1...
Diagonal traversal of a binary tree involves traversing nodes diagonally from top to bottom and left to right.
Traverse the tree level by level, starting from the root node.
For each level, keep track of the diagonal nodes and their children.
Use a queue to store nodes at each level and traverse them accordingly.
Example: For input 1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1, the diagonal traversal is 1 3 6 2 5 4 7.
Number of Islands Problem Statement
You are provided with a 2-dimensional matrix having N rows and M columns, containing only 1s (land) and 0s (water). Your goal is to determine the number of islands in th...
Count the number of islands in a 2D matrix of 1s and 0s.
Use Depth First Search (DFS) or Breadth First Search (BFS) to traverse the matrix and identify connected groups of 1s.
Maintain a visited array to keep track of visited cells to avoid redundant traversal.
Increment the island count each time a new island is encountered.
Consider all eight possible directions for connectivity while traversing the matrix.
Handle ed...
What people are saying about Ola Cabs
OLA app system design involves multiple components like user interface, driver matching algorithm, payment processing, etc.
User interface for booking rides and tracking
Driver matching algorithm based on location and availability
Payment processing for seamless transactions
Real-time tracking of rides for both users and drivers
Missing Numbers Problem Statement
You are provided with an array called ARR, consisting of distinct positive integers. Your task is to identify all the numbers that fall within the range of the smallest an...
Identify missing numbers within the range of smallest and largest elements in an array.
Find the smallest and largest elements in the array.
Generate a list of numbers within this range.
Filter out the numbers present in the array.
Return the missing numbers in sorted order.
Design a toll booth system for Ola cabs with necessary functions and data structures.
Use a queue data structure to manage the order of vehicles waiting at the toll booth.
Implement functions for vehicle entry, toll calculation, and exit.
Store vehicle information such as license plate number, type of vehicle, and toll amount in a hash map.
Utilize a priority queue to handle VIP or premium customers efficiently.
Includ...
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; otherwi...
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 implement the LRU cache.
Keep track of the least recently used item and evict it when the cache reaches its capacity.
Update the position of an item in the cache whenever it is accessed or updated.
Handle both get and put operations efficiently to...
Problem: Permutations of a String
Given a string STR consisting of lowercase English letters, your task is to return all permutations of the given string in lexicographically increasing order.
Explanation...
Return all permutations of a given string in lexicographically increasing order.
Use backtracking to generate all permutations of the string.
Sort the permutations to get them in lexicographically increasing order.
Ensure the string contains unique characters to avoid duplicate permutations.
Find the Kth Row of Pascal's Triangle Problem Statement
Given a non-negative integer 'K', determine the Kth row of Pascal’s Triangle.
Example:
Input:
K = 2
Output:
1 1
Input:
K = 4
Output:
1 4 6 4...
The task is to find the Kth row of Pascal's Triangle given a non-negative integer K.
Create an array to store the elements of the Kth row of Pascal's Triangle.
Use the formula C(n, k) = C(n-1, k-1) + C(n-1, k) to calculate each element in the row.
Return the array containing the Kth row of Pascal's Triangle.
Ola Cabs Software Developer Interview Experiences
5 interviews found
(2 Questions)
- Q1. What is Closure
- Ans.
Closure is a function that captures the environment in which it was created, allowing it to access variables from that environment even after the function has finished executing.
Closure allows a function to access variables from its outer scope even after the function has finished executing.
It is created when a function is defined within another function and the inner function references variables from the outer functi...
- Q2. Flat nested array
(2 Questions)
- Q1. Machine coding questions
- Q2. Das based questions
(2 Questions)
- Q1. Simple questions
- Q2. Simple questions one on one
BIDISHA MISRA
One coding and other mcqs on CS concepts
I appeared for an interview in May 2021.
(2 Questions)
Round duration - 60 minutes
Round difficulty - Medium
This was coding round and was conducted on Google meet with code link shared. Their were 2 interviewers that gave questions and later ran code on sample test cases.
- Q1.
Problem: Permutations of a String
Given a string
STRconsisting of lowercase English letters, your task is to return all permutations of the given string in lexicographically increasing order.Explanatio...
- Ans.
Return all permutations of a given string in lexicographically increasing order.
Use backtracking to generate all permutations of the string.
Sort the permutations to get them in lexicographically increasing order.
Ensure the string contains unique characters to avoid duplicate permutations.
- Q2.
Find the Kth Row of Pascal's Triangle Problem Statement
Given a non-negative integer 'K', determine the Kth row of Pascal’s Triangle.
Example:
Input:
K = 2
Output:
1 1
Input:
K = 4
Output:
1 4 6 ...
- Ans.
The task is to find the Kth row of Pascal's Triangle given a non-negative integer K.
Create an array to store the elements of the Kth row of Pascal's Triangle.
Use the formula C(n, k) = C(n-1, k-1) + C(n-1, k) to calculate each element in the row.
Return the array containing the Kth row of Pascal's Triangle.
Round duration - 90 minutes
Round difficulty - Medium
This was a Machine Coding Round/LLD round followed by HLD round which was taken by Video Conferencing and Screen Sharing.
Round duration - 60 minutes
Round difficulty - Easy
This was the last round. This was HM round followed by the HR round.
Interview Preparation Tips
Tip 1 : Solve previously asked questions. It tells you about the level of questions that the company asks. Check glass-door reviews it will help you to know what kind of questions company ask
Tip 2 : Be real during the interview and don’t show off.
Tip 3 : Prepare for theory subjects like Object-Oriented Programming System, Database Management System, Computer networks, etc.
Tip 1 : Keep your resume simple with all work experience mentioned.
Tip 2 : Any unwanted information on the resume leaves a bad impact on the interviewer.
Tip 3 : You should be prepared to explain anything that’s written on your resume.
Tip 4 : Keep it of 1 page or 2 pages only
Skills evaluated in this interview
I appeared for an interview before May 2021.
(3 Questions)
Round duration - 90 minutes
Round difficulty - Medium
It was in the morning, where there were 3 questions to answer.
- Q1.
Number of Islands Problem Statement
You are provided with a 2-dimensional matrix having
Nrows andMcolumns, containing only 1s (land) and 0s (water). Your goal is to determine the number of islands in t... - Ans.
Count the number of islands in a 2D matrix of 1s and 0s.
Use Depth First Search (DFS) or Breadth First Search (BFS) to traverse the matrix and identify connected groups of 1s.
Maintain a visited array to keep track of visited cells to avoid redundant traversal.
Increment the island count each time a new island is encountered.
Consider all eight possible directions for connectivity while traversing the matrix.
Handle edge ca...
- Q2.
Missing Numbers Problem Statement
You are provided with an array called
ARR, consisting of distinct positive integers. Your task is to identify all the numbers that fall within the range of the smallest a... - Ans.
Identify missing numbers within the range of smallest and largest elements in an array.
Find the smallest and largest elements in the array.
Generate a list of numbers within this range.
Filter out the numbers present in the array.
Return the missing numbers in sorted order.
- Q3.
Count Leaf Nodes in a Binary Tree
Given a binary tree, your task is to count and return the number of leaf nodes present in it.
A binary tree is a data structure where each node has at most two children,...
- Ans.
Count and return the number of leaf nodes in a binary tree.
Traverse the binary tree and count nodes with both left and right children as NULL.
Use recursion to traverse the tree efficiently.
Leaf nodes have no children, so check for NULL left and right children to identify them.
(1 Question)
Round duration - 20 minutes
Round difficulty - Medium
It was a system design round.
- Q1. Can you describe the system design of the OLA app?
- Ans.
OLA app system design involves multiple components like user interface, driver matching algorithm, payment processing, etc.
User interface for booking rides and tracking
Driver matching algorithm based on location and availability
Payment processing for seamless transactions
Real-time tracking of rides for both users and drivers
(2 Questions)
Round duration - 45 minutes
Round difficulty - Medium
It was a DS Algo round.
- Q1.
Diagonal Traversal of a Binary Tree Problem Statement
Given a binary tree, your task is to determine the diagonal traversal of the tree.
Example:
Input:
1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1
Output:
...
- Ans.
Diagonal traversal of a binary tree involves traversing nodes diagonally from top to bottom and left to right.
Traverse the tree level by level, starting from the root node.
For each level, keep track of the diagonal nodes and their children.
Use a queue to store nodes at each level and traverse them accordingly.
Example: For input 1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -1, the diagonal traversal is 1 3 6 2 5 4 7.
- Q2.
Minimum Number Of Taps To Water Garden Problem Statement
You are required to determine the minimum number of taps that need to be opened to water an entire one-dimensional garden defined along the x-axis,...
- Ans.
Find the minimum number of taps to water an entire garden along the x-axis.
Iterate over the taps and find the farthest point each tap can reach.
Sort the taps based on their starting points and use a greedy approach to select the taps.
Keep track of the farthest point reachable by the selected taps and the number of taps opened.
Return the minimum number of taps needed to water the entire garden or -1 if it's impossible.
Round duration - 15 minutes
Round difficulty - Medium
HR Round
Interview Preparation Tips
Tip 1 : Go through standard problems
Tip 2 : You should know about everything you have written on your resume
Tip 1 : Keep it short not more than 1 page.
Tip 2 : Write more about figures and technicality on your resume.
Skills evaluated in this interview
I appeared for an interview before Sep 2020.
Round duration - 45 minutes
Round difficulty - Easy
This round was telephonic round. The interview lasted for approximately 45 minutes. The interviewer asked me three coding questions. I hustled a bit on 3rd question but after a hint was able to solve it.
(1 Question)
Round duration - 120 minutes
Round difficulty - Easy
This round was Online Test on Hackerrank for 120 minutes, it contained 3 questions.
- Q1.
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...
Round duration - 60 minutes
Round difficulty - Easy
This round was face to face Interview at Ola Campus and lasted for 1 hour.
Round duration - 35 minutes
Round difficulty - Easy
This round was again a face to face technical interview, I was just asked one question in this round.
(1 Question)
Round duration - 30 minutes
Round difficulty - Easy
Only a question of System Design was asked
- Q1. Design a toll booth system for Ola cabs and explain the necessary functions and data structures used in it.
- Ans.
Design a toll booth system for Ola cabs with necessary functions and data structures.
Use a queue data structure to manage the order of vehicles waiting at the toll booth.
Implement functions for vehicle entry, toll calculation, and exit.
Store vehicle information such as license plate number, type of vehicle, and toll amount in a hash map.
Utilize a priority queue to handle VIP or premium customers efficiently.
Include a f...
(2 Questions)
Round duration - 30 minutes
Round difficulty - Easy
Very general HR questions were asked
- Q1. What are your strengths and weaknesses?
- Q2. Why do you want to join Ola?
Interview Preparation Tips
Tip 1 : Be confident in the projects you have mentioned in your resume.
Tip 2 : Always discuss your approach with the interviewer first for any problem.
Tip 3 : Always start with a basic solution and then discuss further optimisations.
Tip 1 : Good projects showing your skills (Be clear in what you achieved from those projects)
Tip 2 : Internship experience at the top (It gives you an edge over others)
Skills evaluated in this interview
Interview questions from similar companies
Interview Questionnaire
1 Question
- Q1. They asked 3 Coding questions and 5 MCQ all of them were very simple. One was related to fibbonaci. Another one was like there was 2d array and at i,j sum till row i and sum till j was given and all the el...
Interview Preparation Tips
I appeared for an interview before Jan 2021.
(2 Questions)
Round duration - 60 minutes
Round difficulty - Easy
Two coding questions were given in the first round to be solved in 60 minutes.
- Q1.
Rearrange Array Elements Problem Statement
Given an array
Acontaining 'N' integers and an integerm, rearrange the elements of the array such that the differences between the array elements andmare sor... - Ans.
Rearrange array elements based on their differences from a given integer.
Calculate the differences between each element and the given integer.
Sort the elements based on their differences while maintaining the original order for elements with the same difference.
Implement a function to rearrange the array elements as per the given criteria.
- Q2.
Print Nodes at Distance K from a Given Node
Given an arbitrary binary tree, a node of the tree, and an integer 'K', find all nodes that are at a distance K from the specified node, and return a list of th...
(4 Questions)
Round duration - 60 minutes
Round difficulty - Easy
This was a technical round with questions based on DSA, DBMS, Computer Networking and project based questions.
- Q1.
Triangle of Numbers Pattern
Ninja is tasked with printing a triangle pattern based on a given number 'N' for any test case.
Example:
Input:
N = 4
Output:
1
232
34545
4567654Explanation:
The pat...
- Ans.
Print a triangle pattern of numbers based on a given number 'N'.
Iterate through each row and print the numbers accordingly
Use spaces to center-align the numbers in each row
Increment the numbers in each row as per the pattern
- Q2. What is the difference between a web server and an application server?
- Q3. How does the internet work?
- Ans.
The internet is a global network of interconnected computers that communicate using standardized protocols.
The internet is made up of a vast number of interconnected networks of computers.
Data is transmitted over the internet using protocols such as TCP/IP.
Websites are hosted on servers connected to the internet, and users access them using web browsers.
Internet Service Providers (ISPs) provide access to the internet f...
- Q4. Write a SQL query to find the nth highest salary.
Round duration - 30 minutes
Round difficulty - Easy
Typical HR round with behavioral problems.
Interview Preparation Tips
Tip 1 : Must do Previously asked Interview as well as Online Test Questions.
Tip 2 : Go through all the previous interview experiences from Codestudio and Leetcode.
Tip 3 : Do at-least 2 good projects and you must know every bit of them.
Tip 1 : Have at-least 2 good projects explained in short with all important points covered.
Tip 2 : Every skill must be mentioned.
Tip 3 : Focus on skills, projects and experiences more.
Skills evaluated in this interview
I appeared for an interview before Dec 2020.
(2 Questions)
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...
- 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 ...
- 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...
(1 Question)
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
AandBwith sizesNandMrespectively, both sorted in non-decreasing order, determine their intersection.The intersection of two arrays in...
- 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.
Interview Preparation Tips
Tip 1 : Must do Previously asked Interview as well as Online Test Questions.
Tip 2 : Go through all the previous interview experiences from Codestudio and Leetcode.
Tip 3 : Do at-least 2 good projects and you must know every bit of them.
Tip 1 : Have at-least 2 good projects explained in short with all important points covered.
Tip 2 : Every skill must be mentioned.
Tip 3 : Focus on skills, projects and experiences more.
Skills evaluated in this interview
Software Developer Interview Questions & Answers
Eternal Limited
Gulshan Kumar
posted on 30 Nov 2015
I applied via Campus Placement
Interview Preparation Tips
Experience: They selected 10 students from our college from CS and IT .They are looking for guys with extra projects done during college .App development will be a bonus ,contribution to open source and competitive programming will help for shortlisting.
Some of my friends had research papers published and they too got selected.
Round: Test
Experience: Have to write code snippet for 4 questions in 45 minutes
1.Difference between hour hand and minute hand
2.longest palindromic sub string.
3.Product Array puzzle
4.Some question related to matrix
Tips: All question were from geeksforgeeks
So practice it well ..u will make through it
Round: Test
Experience: Long Discussion on projects
They will scan each and every line of your Resume ,so dont write bullshits..
I wrote about interest in AI and got screwed..Discussion on college projects and final year project.
Then asked me to design a snake and ladder game OOPS concepts
Told me to find sum of all elements of sub matrix..(hint pre-processing the matrix)
Asked me about sessions and cookies
Gave a query to write on database indexing (dont remember exactly)
Asked me the code of the difference between hour hand and minute hand and extended it wid the second hand
Asked me as how to implement a dictionary
asked about TRIES ,CODE SNIPPET ON THE SHARED DOCS
One of my friend was asked to implement (set) of STL
Tips: The interviewer was cool guy..helped me a lot always made me comfortable.Interact with them as much as possible
Round: Test
Experience: Wid the CTO of the company .
Started wid the projects again .ACID properties,Database transactions,Concurrency Control
Optimization in database.
Then he asked me to code a function
Given a hash function applied on letters of English words ,un-hash it.Took me 45 minutes to reach the solution ,he helped me a lot.
Asked me to write the code for diameter of a binary tree
Asked me write the code for Boolean Matrix
One of my friend was asked to a question in which there was a bug in a m*n matrix and we have to find the bug(hint dfs or bfs)
Tips: keep calm ,,just keep talking ad he will help u a lot...
Round: HR
Experience: This was the toughest round for me...I had cleared all the rounds but they rejected me in the HR round ,,,dont know where I screwed..Learn every thing of Zomato..
They offered me an internship and thereafter they would look to give a PPO ...!!!lets see what happens
Skills: Coding Skills And Knowledge On Data Structures
Duration: 3
College Name: NIT Srinagar
I appeared for an interview before Jan 2021.
(3 Questions)
Round duration - 60 Minutes
Round difficulty - Medium
This was a typical DS/Algo where I was asked to solve two questions related to Binary Trees and write the pseudo code for both of them followed by some theoretical questions related to Operating Systems.
- Q1.
K-th Largest Number in a BST
Given a binary search tree (BST) consisting of integers and containing 'N' nodes, your task is to find and return the K-th largest element in this BST.
If there is no K-th la...
- Q2.
Is Height Balanced Binary Tree Problem Statement
Determine if the given binary tree is height-balanced. A tree is considered height-balanced when:
- The left subtree is balanced.
- The right subtree is bala...
- Q3. Can you explain the concepts of Zombie Process and Orphan Process in operating systems?
- Ans.
Zombie process is a terminated process that has completed execution but still has an entry in the process table. Orphan process is a process whose parent process has terminated.
Zombie process is created when a child process completes execution but its parent process has not yet read its exit status.
Zombie processes consume system resources and should be cleaned up by the parent process using wait() system call.
Orphan p...
(3 Questions)
Round duration - 60 Minutes
Round difficulty - Medium
This was also a Data Structures and Algorithm round where I was asked to solve 3 medium to hard level problems along with their pseudo code within 60 minutes .
- Q1.
Longest Substring Without Repeating Characters Problem Statement
Given a string
Sof lengthL, determine the length of the longest substring that contains no repeating characters.Example:
Input:
"abac...
- Q2.
Problem: Search In Rotated Sorted Array
Given a sorted array that has been rotated clockwise by an unknown amount, you need to answer
Qqueries. Each query is represented by an integerQ[i], and you must ... - Q3.
Count Subarrays with Sum Divisible by K
Given an array
ARRand an integerK, your task is to count all subarrays whose sum is divisible by the given integerK.Input:
The first line of input contains an...
(2 Questions)
Round duration - 50 Minutes
Round difficulty - Medium
In this round , I was asked to code a simple question related to BST . After that I was asked the internal implementation of a Hash Map where I was supposed to design a Hash Map using any of the Hashing Algorithms that I know . This was preety challenging for me but I got to learn so much from it.
- Q1.
Ceil Value from BST Problem Statement
Given a Binary Search Tree (BST) and an integer, write a function to return the ceil value of a particular key in the BST.
The ceil of an integer is defined as the s...
- Q2.
Design a Constant Time Data Structure
Create a data structure that maintains mappings between keys and values, supporting the following operations in constant time:
1. INSERT(key, value): Add or update t...
Interview Preparation Tips
Tip 1 : Must do Previously asked Interview as well as Online Test Questions.
Tip 2 : Go through all the previous interview experiences from Codestudio and Leetcode.
Tip 3 : Do at-least 2 good projects and you must know every bit of them.
Tip 1 : Have at-least 2 good projects explained in short with all important points covered.
Tip 2 : Every skill must be mentioned.
Tip 3 : Focus on skills, projects and experiences more.
Skills evaluated in this interview
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