Zolo Software Developer Intern Interview Questions and Answers

Round duration - 45 minutes
Round difficulty - Easy

This was a test where 2 coding questions were to be solved in 45 minutes.

Q1. 
Excel Column Number Conversion
Given a column title as it appears in an Excel sheet, your task is to return its corresponding column number.
Example:
Input:
S = "AB"
Output:
28
Explanation:
The seq...read more
Ans. 
Convert Excel column title to corresponding column number.
• Iterate through the characters in the input string from right to left

• Calculate the value of each character based on its position and multiply by 26^index

• Sum up the values to get the final column number
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Q2. 
Check Permutation Problem
Determine if two given strings, str1 and str2, are permutations of each other.
Explanation:
Two strings are permutations of each other if the characters of one string can be re...read more
Ans. 
Check if two strings are permutations of each other.
• Create character frequency maps for both strings.

• Compare the frequency maps to check if they are permutations.

• Handle edge cases like empty strings or strings of different lengths.
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Q1. Launch modes on android
Ans. 
Launch modes on Android determine how a new instance of an activity is associated with the current task.
• Standard: Creates a new instance of the activity in the task's stack

• SingleTop: If an instance of the activity already exists at the top of the stack, it will not be recreated

• SingleTask: Activity is always at the root of the task and no other activities can be on top of it

• SingleInstance: Similar to SingleTask, but the
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Questios based on Activity backstacks

Data structure - rainwater trapping

Q1. OOPs concept, core java, sql
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Q2. Car parking lot problem - system design
Ans. 
Design a car parking lot system
• Determine the size and capacity of the parking lot

• Create a database to store information about available spots and occupied spots

• Develop a system to track the entry and exit of vehicles

• Implement a payment system for parking fees

• Incorporate security measures such as CCTV cameras and security personnel

• Provide a user-friendly interface for customers to locate available spots and make payment
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Q1. Rapid fire questions
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Q2. More java springboot
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Basic JavaScript Interview

Q1. What is closure
Ans. 
Closure is a function that has access to its own scope, as well as the outer scope in which it was defined.
• Closure allows a function to access variables from its outer scope even after the outer function has finished executing.

• It is created whenever a function is defined within another function.

• Closure is commonly used in JavaScript for maintaining state in asynchronous operations.
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Q2. What are promise
Ans. 
Promises are objects representing the eventual completion or failure of an asynchronous operation.
• Promises are used to handle asynchronous operations in JavaScript.

• They can be in one of three states: pending, fulfilled, or rejected.

• Promises can be chained together using .then() method.

• They help avoid callback hell and make code more readable.

• Example: Fetching data from an API returns a promise that resolves with the da
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Q1. Introduce yourself
Ans. 
I am a software developer with 5 years of experience in Java and Python. I have a passion for problem-solving and creating innovative solutions.
• 5 years of experience in Java and Python

• Passionate about problem-solving

• Innovative solutions driven
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Q2. Were u see after 5 years
Ans. 
In 5 years, I see myself as a senior software developer leading a team and working on cutting-edge technologies.
• Leading a team of developers on innovative projects

• Working with cutting-edge technologies like AI and blockchain

• Continuing to learn and grow in my career

• Possibly pursuing further education or certifications

• Contributing to open source projects
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HAckerrank based test

Round duration - 60 Minutes
Round difficulty - Easy

4 Questions which were of Easy, Medium, and Hard level.

Q1. 
Lowest Common Ancestor of a Binary Tree III
The structure of a binary tree has been modified so that each node includes a reference to its parent node.
Problem Statement
You are provided with two nodes,...read more
Ans. 
This question is about finding the lowest common ancestor of two nodes in a binary tree with parent references.
• Traverse from the given nodes to their respective root nodes and store the paths in two separate lists.

• Compare the two lists and find the last common node.

• Return the last common node as the lowest common ancestor.
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Q2. 
Maximum Subarray Problem Statement
Ninja has been given an array, and he wants to find a subarray such that the sum of all elements in the subarray is maximum.
A subarray 'A' is considered greater than a...read more
Ans. 
The problem is to find a subarray with the maximum sum in a given array.
• Iterate through the array and keep track of the maximum sum and the current sum.

• If the current sum becomes negative, reset it to 0.

• Update the maximum sum if the current sum is greater.

• Also keep track of the start and end indices of the subarray with the maximum sum.

• Return the subarray using the start and end indices.
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Round duration - 50 Minutes
Round difficulty - Easy

Q1. 
Next Greater Element Problem Statement
Given a list of integers of size N, your task is to determine the Next Greater Element (NGE) for every element. The Next Greater Element for an element X is the firs...read more
Ans. 
The task is to find the next greater element for each element in an array.
• Iterate through the array from right to left.

• Use a stack to keep track of the elements that have a greater element to their right.

• For each element, pop elements from the stack until a greater element is found or the stack is empty.

• If a greater element is found, it is the next greater element for the current element.

• If the stack becomes empty, the...read more
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Q2. 
Trapping Rain Water Problem Statement
You are given a long type array/list ARR of size N, representing an elevation map. The value ARR[i] denotes the elevation of the ith bar. Your task is to determine th...read more
Ans. 
The question asks to find the total amount of rainwater that can be trapped in the given elevation map.
• Iterate through the array and find the maximum height on the left and right side of each bar.

• Calculate the amount of water that can be trapped at each bar by taking the minimum of the maximum heights on both sides and subtracting the height of the bar.

• Sum up the amount of water trapped at each bar to get the total amo
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Round duration - 30 Minutes
Round difficulty - Easy

It is just a formality round, asked basic questions like relocation and joining date etc

Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
0/1 Knapsack Problem Statement
A thief is planning to rob a store and can carry a maximum weight of 'W' in his knapsack. The store contains 'N' items where the ith item has a weight of 'wi' and a value of...read more
Ans. 
Yes, the 0/1 Knapsack problem can be solved using dynamic programming with a space complexity of not more than O(W).
• Use a 1D array to store the maximum value that can be stolen for each weight capacity from 0 to W.

• Iterate through each item and update the array based on whether including the item would increase the total value.

• The final value in the array at index W will be the maximum value that can be stolen.
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Q2. 
Find the Second Largest Element
Given an array or list of integers 'ARR', identify the second largest element in 'ARR'.
If a second largest element does not exist, return -1.
Example:
Input:
ARR = [2,...read more
Ans. 
Find the second largest element in an array of integers.
• Iterate through the array to find the largest and second largest elements.

• Handle cases where all elements are identical.

• Return -1 if a second largest element does not exist.
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Round duration - 60 Minutes
Round difficulty - Easy

System Design Round

Q1. Design a system for Twitter, discussing its architecture, key components, and scalability considerations.
Ans. 
Design a scalable system for Twitter with key components and architecture.
• Use microservices architecture for scalability and fault isolation.

• Key components include user service, tweet service, timeline service, and notification service.

• Use a distributed database like Cassandra for storing tweets and user data.

• Implement a message queue like Kafka for handling real-time updates and notifications.

• Use a caching layer like ...read more
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Round duration - 30 Minutes
Round difficulty - Easy

It is just a formality