OLX Software Developer Interview Questions, Process, and Tips

Round duration - 25 Minutes
Round difficulty - Medium

Very friendly interviewer. Although waiting time was very high

Q1. 
Pair Sum Problem Statement
You are given an integer array 'ARR' of size 'N' and an integer 'S'. Your task is to find and return a list of all pairs of elements where each sum of a pair equals 'S'.
Note:
...read more
Ans. 
Find pairs of elements in an array that sum up to a given value, sorted in a specific order.
• Iterate through the array and for each element, check if the complement (S - current element) exists in a hash set.

• If the complement exists, add the pair to the result list.

• Sort the result list based on the criteria mentioned in the question.

• Return the sorted list of pairs.
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Round duration - 90 minutes
Round difficulty - Easy

This is a written round on paper for everyone. Three coding questions were given. Two out of three must be correct covering every single edge case to qualify for the next round. Only the most optimal solution was to be considered. 

Q1. 
Maximum Subarray Sum Problem Statement
Given an array arr of length N consisting of integers, find the sum of the subarray (including empty subarray) with the maximum sum among all subarrays.
Explanation...read more
Ans. 
Find the sum of the subarray with the maximum sum among all subarrays in an array of integers.
• Iterate through the array and keep track of the maximum sum subarray encountered so far.

• Use Kadane's algorithm to efficiently find the maximum subarray sum.

• Consider the sum of an empty subarray as 0.

• Example: For input arr = [-2, 1, -3, 4, -1], the maximum subarray sum is 4.
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Q2. 
Connecting Ropes with Minimum Cost
You are given 'N' ropes, each of varying lengths. The task is to connect all ropes into one single rope. The cost of connecting two ropes is the sum of their lengths. Yo...read more
Ans. 
Connect ropes with minimum cost by merging two smallest ropes at a time.
• Sort the array of rope lengths in ascending order.

• Merge the two smallest ropes at a time and update the cost.

• Repeat the process until all ropes are merged.

• Return the total cost as the minimum cost to connect all ropes.
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Q3. 
Left View of a Binary Tree Problem Statement
Given a binary tree, your task is to print the left view of the tree.
Example:
Input:
The input will be in level order form, with node values separated by a...read more
Ans. 
Print the left view of a binary tree given in level order form.
• Traverse the tree level by level and print the first node encountered at each level

• Use a queue to perform level order traversal

• Keep track of the level while traversing the tree
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Round duration - 50 minutes
Round difficulty - Easy

This was face to face interview round.

Q1. 
Finding Triplets in a Binary Tree Problem Statement
You are given a Binary Tree of integers and an integer 'X'. Your task is to find all the triplets in the tree whose sum is strictly greater than 'X'. Th...read more
Ans. 
Find all triplets in a binary tree whose sum is greater than a given integer X, with a grandparent-parent-child relationship.
• Traverse the binary tree to find all possible triplets with the required relationship.

• Keep track of the sum of each triplet and compare it with the given integer X.

• Return the triplets that satisfy the condition in any order.

• Ensure each triplet follows the format (grand-parent, parent, child).
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Q2. 
Loot Houses Problem Statement
A thief is planning to steal from several houses along a street. Each house has a certain amount of money stashed. However, the thief cannot loot two adjacent houses. Determi...read more
Ans. 
Determine the maximum amount of money a thief can steal from houses without looting two consecutive houses.
• Use dynamic programming to keep track of the maximum amount of money that can be stolen up to each house.

• At each house, the thief can either choose to steal from the current house or skip it and steal from the previous house.

• The maximum amount of money that can be stolen at the current house is the maximum of the ...read more
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Round duration - 60 minutes
Round difficulty - Easy

This was face to face interview round.

Round duration - 90 Minutes
Round difficulty - Medium

This is a written round on paper for everyone. Three coding questions were given. Two out of three must be correct covering every single edge case to qualify for the next round. Only the most optimal solution was to be considered.

Q1. 
Maximum Subarray Sum Problem Statement
Given an array ARR consisting of N integers, your goal is to determine the maximum possible sum of a non-empty contiguous subarray within this array.
Example of Sub...read more
Ans. 
Find the maximum sum of a contiguous subarray in an array of integers.
• Use Kadane's algorithm to find the maximum subarray sum in linear time.

• Initialize two variables: maxSum and currentSum.

• Iterate through the array and update currentSum by adding the current element or starting a new subarray.

• Update maxSum if currentSum becomes greater than maxSum.

• Return maxSum as the maximum subarray sum.
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Round duration - 50 Minutes
Round difficulty - Easy

This was face to face interview round.

Q1. 
Finding Triplets in a Binary Tree Problem Statement
You are given a Binary Tree of integers and an integer 'X'. Your task is to find all the triplets in the tree whose sum is strictly greater than 'X'. Th...read more
Ans. 
Find all triplets in a binary tree whose sum is greater than a given integer X, with a grandparent-parent-child relationship.
• Traverse the binary tree to find all possible triplets.

• Check if the sum of each triplet is greater than X.

• Ensure the relationship of grandparent-parent-child in each triplet.

• Return the valid triplets in any order.

• Handle constraints and edge cases appropriately.
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Round duration - 60 Minutes
Round difficulty - Easy

FACE TO FACE ROUND INTERVIEW

Q1. Can you tell me about yourself?
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Q2. What is the difference between Mutex and Semaphores? Please provide a real-life example.
Ans. 
Mutex is used for exclusive access to a resource by only one thread at a time, while Semaphores can allow multiple threads to access a resource simultaneously.
• Mutex is binary and allows only one thread to access a resource at a time, while Semaphores can have a count greater than one.

• Mutex is used for protecting critical sections of code, while Semaphores can be used for controlling access to a pool of resources.

• Exampl...read more
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