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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...
One coding and other mcqs on CS concepts
I was interviewed in May 2021.
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.
Given a string STR
consisting of lowercase English letters, your task is to return all permutations of the given string in lexicographically increasing order.
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.
Given a non-negative integer 'K', determine the Kth row of Pascal’s Triangle.
K = 2
1 1
K = 4
1 4 6 ...
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.
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
I was interviewed before May 2021.
Round duration - 90 minutes
Round difficulty - Medium
It was in the morning, where there were 3 questions to answer.
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 t...
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...
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...
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.
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.
Round duration - 20 minutes
Round difficulty - Medium
It was a system design round.
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
Round duration - 45 minutes
Round difficulty - Medium
It was a DS Algo round.
Given a binary tree, your task is to determine the diagonal traversal of the tree.
1 2 3 4 -1 5 6 -1 7 -1 -1 -1 -1 -1 -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.
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 impossible.
Round duration - 15 minutes
Round difficulty - Medium
HR Round
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.
Ola Cabs interview questions for designations
I was interviewed 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.
Round duration - 120 minutes
Round difficulty - Easy
This round was Online Test on Hackerrank for 120 minutes, it contained 3 questions.
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...
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 main...
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.
Round duration - 30 minutes
Round difficulty - Easy
Only a question of System Design was asked
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...
Round duration - 30 minutes
Round difficulty - Easy
Very general HR questions were asked
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)
Get interview-ready with Top Ola Cabs Interview Questions
Top trending discussions
I was interviewed before Sep 2020.
Round duration - 180 minutes
Round difficulty - Medium
The online test consisted of 2 coding questions, 30 aptitude MCQs, 30 behavioral MCQs and 10 code snippets to debug. The coding questions were of medium level, aptitude MCQs were easy and the code snippets to debug was also of easy level. Each section had a time constraint.
You are provided with two sorted linked lists. Your task is to merge them into a single sorted linked list and return the head of the combined linked list.
...Merge two sorted linked lists into a single sorted linked list without using additional space beyond constant space complexity.
Create a dummy node to start the merged list
Iterate through both linked lists and compare nodes to merge them in sorted order
Update the next pointers accordingly
Handle cases where one list is empty or both lists are empty
Return the head of the merged linked list
Consider a 2-dimensional grid 'GRID' with 'N' rows and 'M' columns in Ninjaland. Each cell in the grid has an associated cost. The goal is to determine the minimum path ...
The Minimum Path Sum Problem involves finding the minimum sum of costs along a path from the top-left to the bottom-right of a grid.
Use dynamic programming to calculate the minimum path sum by considering the costs of moving down or right at each cell.
Initialize a 2D array to store the minimum path sum values for each cell in the grid.
Iterate through the grid to calculate the minimum path sum for each cell based on the...
Round duration - 60 minutes
Round difficulty - Medium
My interview was at 9:00 am. The interview was conducted on Amazon Chime and my webcam was on. The interviewer also asked me to write the code on a document which can be edited by both me and the interviewer. The difficulty of the questions was of medium level. I was asked 3 coding questions along with 2 questions related to OOPS at the end. The interview ended with the discussion of one of my projects. The interviewer was good and also gave me hints wherever required.
You are given a string S
. Your task is to partition S
such that every substring of the partition is a palindrome. Your objective is to return all possible palindr...
Given a string, partition it into palindromes and return all possible configurations.
Use backtracking to generate all possible palindrome partitions
Check if each substring is a palindrome before adding it to the partition
Return all valid partitions as an array of strings
Given an array of integers with 'N' elements, determine the length of the longest subsequence where each element is greater than the previous element. This...
Find the length of the longest strictly increasing subsequence in an array of integers.
Use dynamic programming to solve this problem efficiently.
Initialize an array to store the length of the longest increasing subsequence ending at each index.
Iterate through the array and update the length of the longest increasing subsequence for each element.
Return the maximum value in the array as the result.
You have a sequence of consecutive nonnegative integers. By appending all integers end-to-end, you formed a string S
without any separators. During this pro...
Find the missing number in a string of consecutive nonnegative integers.
Iterate through the string and check for missing numbers by comparing adjacent integers
If a missing number is found, return it as the output
Handle cases where there are multiple missing numbers or the string is invalid by returning -1
ACID properties in DBMS ensure data integrity and consistency.
Atomicity: All operations in a transaction are treated as a single unit of work, either all succeed or all fail.
Consistency: Database remains in a consistent state before and after the transaction.
Isolation: Transactions are isolated from each other until they are completed.
Durability: Once a transaction is committed, the changes made by it are permanent and...
Tip 1 : You must have a grip over Data Structures and algorithms. Your concepts must be crystal clear. Pick one coding platform and try to practice at least 7-10 coding questions everyday. I completed around 200+ questions on Leetcode, 200+ questions on Geek For Geeks and around 30-40 questions on InterviewBit.
Tip 2 : After attempting any coding problem, analyze its time and space complexity. See, if you can further optimize your solution. You can always check the editorials and compare your solution with it.
Tip 3 : Apart from coding questions keep studying concepts of Operating Systems, databases and object oriented programming. You can always refer to Geeks For Geeks articles for it. Also, Coding Ninja's Data Structures and algorithms course in C++ helped me a lot in improving my OOPS concepts specifically.
Tip 1 : You do not need to have a long list of projects on your resume. One good project with proper knowledge of it will do good. Similarly, do not list down several number of skills. Few skills but roper knowledge of them are enough.
Tip 2 : Do not fake anything on your resume. The interviewer gets to know about it by asking questions. If you aren't able to answer, it leaves a negative impact.
I was interviewed before Sep 2020.
Round duration - 90 minutes
Round difficulty - Easy
This was MCQ+Coding round.
Check if two strings are anagrams by comparing the sorted versions of the strings.
Sort both strings and compare if they are equal.
Use a hashmap to store the frequency of characters in each string and compare the maps.
Ignore spaces and punctuation when comparing the strings.
Round duration - 90 minutes
Round difficulty - Easy
This was face to face interview round.
Round duration - 90 minutes
Round difficulty - Easy
This was face to face interview round.
Tip 1 : Participate in live contests on websites like Codechef, Codeforces etc as much as possible.
Tip 2 : Practice previous interview questions from LeetCode, GeeksForGeeks.
Tip 3 : Revise Computer Science subjects like DBMS, OOPS thoroughly.
Add projects and Internships if you have done any and add only those things which you really know.
Final outcome of the interviewSelectedI was interviewed before Sep 2020.
Round duration - 90 Minutes
Round difficulty - Medium
Interview started at 11:00 am. It was an online round. During the coding round I submitted optimized solution and got full acceptance of the solutions.
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...
Detect cycle in a directed graph using depth-first search (DFS) algorithm.
Use DFS to traverse the graph and detect back edges indicating a cycle.
Maintain a visited array to keep track of visited nodes during traversal.
If a node is visited again during traversal and it is not the parent node, then a cycle exists.
Return true if a cycle is detected, false otherwise.
Round duration - 80 Minutes
Round difficulty - Medium
Interview started at 10:00 am. Interview went well, I was able to connect with the interviewer and enjoyed the whole interview
Find the next smallest palindrome strictly greater than a given number 'N' represented as a string 'S'.
You are given a number in string format, a...
Find the next smallest palindrome greater than a given number represented as a string.
Convert the string to an integer, find the next greater palindrome, and convert it back to a string.
Handle cases where the number is a palindrome or has all digits as '9'.
Consider both odd and even length numbers when finding the next palindrome.
Round duration - 80 Minutes
Round difficulty - Medium
Interview started at 11:00 am. Interview went well.
Given a binary tree of integers, your task is to return the boundary nodes of the tree in Anti-Clockwise direction starting from the root node.
The first line ...
Return the boundary nodes of a binary tree in Anti-Clockwise direction starting from the root node.
Traverse the left boundary nodes in a top-down manner
Traverse the leaf nodes from left to right
Traverse the right boundary nodes in a bottom-up manner
Handle cases where duplicates occur in the boundary nodes
Implement the function without printing as printing is already managed
Tip 1 : For Data Structures number of questions doesn't matter. Try to understand the logic behind them and try to apply them in creating multiple scenario's. Learn them by heart.
Tip 2 : For Web.Development Try to learn full stack development. See which part interests you more, Increase your knowledge horizon, Always try to build a system a system considering It will be served to millions of customers. By doing this 1-2 projects will increase and cover all the major things which one should learn in their career/college.
Tip 1 : Always try to make it a single page
Tip 2 : Always make resume company specific. eg. Data Structures part more if you are applying for MNC's eg. Amazon, Google, DE Shaw, browserstack.
I was interviewed in Oct 2020.
Round duration - 120 minutes
Round difficulty - Medium
Evening test around 5
Platform :- SHL
Environment was amazing
Given two binary trees, T and S, determine whether S is a subtree of T. The tree S should have the same structure and node values as a subtree of T.
Given two binary trees T and S, determine if S is a subtree of T with the same structure and node values.
Check if the second tree is a subtree of the first tree by comparing their structures and node values.
Use a recursive approach to traverse both trees and check for equality.
Handle cases where one tree is null or the values do not match.
Return true if S is a subtree of T, false otherwise.
You are given an N * N matrix of integers where each row and each column is sorted in increasing order. Your task is to find the positi...
Given a sorted N*N matrix, find the position of a target integer X.
Iterate over each row and column to find the target integer X
Utilize the sorted nature of the matrix to optimize the search process
Return the position of X if found, else return -1 -1
Round duration - 60 minutes
Round difficulty - Medium
1 Hour
Afternoon
You are provided with two singly linked lists containing integers, where both lists converge at some node belonging to a third linked list.
Your task is to determine t...
Find the node where two linked lists merge, return -1 if no merging occurs.
Traverse both lists to find their lengths and the difference in lengths
Move the pointer of the longer list by the difference in lengths
Traverse both lists simultaneously until they meet at the merging point
Given a Binary Search Tree (BST) and an integer 'S', your task is to find all pairs of nodes within the BST that total to 'S' and return these pairs. If no such p...
Find pairs of nodes in a BST that sum up to a given value 'S'.
Traverse the BST in-order to get a sorted list of nodes.
Use two pointers approach to find pairs with sum 'S'.
Keep track of visited nodes to avoid using the same node twice in a pair.
Round duration - 60 minutes
Round difficulty - Medium
Online Round held on Chime
You are given a binary tree of integers. Your task is to determine if it is a binary heap tree or not.
The first line of input contains an integer ‘T’ denoti...
Determine if a given binary tree is a binary heap tree or not based on certain properties.
Check if the binary tree is a complete binary tree where every level, except the last level, is completely filled and the last level is as far left as possible.
Ensure that every parent node is greater than all its children nodes, forming a max-heap.
If any node does not have a left or right child, it should be represented as -1 in
Given two strings S
and T
with lengths N
and M
respectively, your task is to find the "Edit Distance" between these strings.
The Edit Distance is defined as the minimum nu...
The task is to find the minimum number of operations required to convert one string into another using delete, replace, and insert operations.
Use dynamic programming to solve the problem efficiently.
Create a 2D array to store the edit distances between substrings of the two input strings.
Fill up the array based on the minimum of three possible operations: insert, delete, or replace.
The final answer will be the value at...
Tip 1 : 1 Programming Language
Tip 2 : Practice Data Structures with atleast 300 ques.
Tip 3 : CS Fundamental
Tip 1 : 1 Pager
Tip 2 : Add top 3 projects in Resume.
I was interviewed in Aug 2017.
Merge Sort is a divide and conquer algorithm that sorts an array by dividing it into two halves, sorting them separately, and then merging the sorted halves.
Divide the array into two halves
Recursively sort the two halves
Merge the sorted halves
Find pairs of integers in a BST whose sum is equal to a given number.
Traverse the BST and store the values in a hash set.
For each node, check if (X - node.value) exists in the hash set.
If yes, add the pair (node.value, X - node.value) to the result.
Continue traversal until all nodes are processed.
Merge overlapping time intervals into mutually exclusive intervals.
Sort the intervals based on their start time.
Iterate through the intervals and merge overlapping intervals.
Output the mutually exclusive intervals.
Example: [(1,3), (2,6), (8,10), (15,18)] -> [(1,6), (8,10), (15,18)]
Different types of hashing and alternative for Linear Chaining
Different types of hashing include division, multiplication, and universal hashing
Alternative for Linear Chaining is Open Addressing
Open Addressing includes Linear Probing, Quadratic Probing, and Double Hashing
An AVL tree is a self-balancing binary search tree where the heights of the left and right subtrees differ by at most one.
AVL tree is a binary search tree with additional balance factor for each node.
The balance factor is the difference between the heights of the left and right subtrees.
Insertion and deletion operations in AVL tree maintain the balance factor to ensure the tree remains balanced.
Rotations are performed ...
Find the minimum number of squares whose sum equals to a given number n.
Use dynamic programming to solve the problem efficiently.
Start with finding the square root of n and check if it is a perfect square.
If not, then try to find the minimum number of squares required for the remaining number.
Repeat the process until the remaining number becomes 0.
Return the minimum number of squares required for the given number n.
Insertion sort for a singly linked list.
Traverse the list and compare each node with the previous nodes
If the current node is smaller, swap it with the previous node
Repeat until the end of the list is reached
Time complexity is O(n^2)
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