Ola Cabs Software Developer Interview Questions, Process, and Tips

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...read more
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Q2. Flat nested array
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Q1. Machine coding questions
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Q2. Das based questions
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Q1. Simple questions
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Q2. Simple questions one on one
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One coding and other mcqs on CS concepts

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 STR consisting of lowercase English letters, your task is to return all permutations of the given string in lexicographically increasing order.
Explanatio...read more
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.
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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 ...read more
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.
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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.

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 N rows and M columns, containing only 1s (land) and 0s (water). Your goal is to determine the number of islands in t...read more
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...read more
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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...read more
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.
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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,...read more
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.
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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
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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:
...read more
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.
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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,...read more
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.
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Round duration - 15 minutes
Round difficulty - Medium

HR Round