Visa Staff Engineer Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Easy

Technical Interview Round with questions based on Data structures, OOPS and SQL.

Q1. 
Delete a Node from a Linked List
You are provided with a linked list of integers. Your task is to implement a function that deletes a node located at a specified position 'POS'.
Input:
The first line co...read more
Ans. 
Implement a function to delete a node from a linked list at a specified position.
• Traverse the linked list to find the node at the specified position.

• Update the pointers of the previous and next nodes to skip the node to be deleted.

• Handle edge cases such as deleting the head or tail of the linked list.

• Ensure to free the memory of the deleted node to avoid memory leaks.
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Q2. Write an SQL query to find the nth highest salary.
Ans. 
SQL query to find the nth highest salary
• Use the ORDER BY clause to sort salaries in descending order

• Use the LIMIT and OFFSET clauses to skip the first n-1 highest salaries

• Combine the above steps in a single query to find the nth highest salary
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Q3. Can you explain the concepts of Object-Oriented Programming (OOP)?
Ans. 
OOP is a programming paradigm based on the concept of objects, which can contain data in the form of fields and code in the form of procedures.
• OOP focuses on creating objects that interact with each other to solve problems.

• Key concepts include encapsulation, inheritance, and polymorphism.

• Encapsulation involves bundling data and methods that operate on the data into a single unit.

• Inheritance allows classes to inherit at...read more
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Round duration - 60 minutes
Round difficulty - Easy

Was asked me about my favorite technologies, What i liked about Facebook. And asked me to design a cinema ticket reservation web site­ like the one satyam has.

Q1. 
Kth Largest Element Problem
Given an array containing N distinct positive integers and a number K, determine the Kth largest element in the array.
Example:
Input:
N = 6, K = 3, array = [2, 1, 5, 6, 3, ...read more
Ans. 
Find the Kth largest element in an array of distinct positive integers.
• Sort the array in non-increasing order and return the Kth element.

• Handle multiple test cases efficiently.

• Ensure all elements in the array are distinct.
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Q2. What are virtual functions?
Ans. 
Virtual functions are functions in a base class that are overridden in derived classes to achieve runtime polymorphism.
• Virtual functions are declared in a base class with the 'virtual' keyword.

• They are overridden in derived classes using the 'override' keyword.

• They allow a function to be called based on the runtime type of an object.

• Virtual functions enable dynamic binding and late binding in C++.

• Example: virtual void ...read more
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Q3. Design a Cinema Ticket Reservation System.
Ans. 
Design a Cinema Ticket Reservation System
• Use a database to store movie information, showtimes, and seat availability

• Allow users to search for movies, select showtimes, and choose seats

• Implement a payment system for ticket purchases

• Send confirmation emails with QR codes for ticket validation
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Q4. In how many attempts can you find a defective ball among 10 given balls using a two-pan balance scale?
Ans. 
You can find a defective ball among 10 given balls in 2 attempts using a two-pan balance scale.
• Divide the 10 balls into two groups of 5 each.

• Weigh the two groups on the balance scale.

• If one group is heavier, it contains the defective ball. If they are equal, the defective ball is in the remaining 5 balls.

• Divide the group of 5 balls with the defective one into two groups of 2 and 3 balls.

• Weigh the two groups on the bala...read more
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Round duration - 30 minutes
Round difficulty - Easy

HR round that lasted for about 30 minutes. The interviewer asked me questions to know more about me and a puzzle.

Q1. Can you tell me about your projects and your extracurricular activities?
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Round duration - 60 minutes
Round difficulty - Easy

I couldn't find an optimal approach to the first question, so she skipped that question and proceeded to next questions. Remaining questions I have answered satisfactorily.

Q1. 
Subset Sum Equal To K Problem Statement
Given an array/list of positive integers and an integer K, determine if there exists a subset whose sum equals K.
Provide true if such a subset exists, otherwise r...read more
Ans. 
Given an array of positive integers and an integer K, determine if there exists a subset whose sum equals K.
• Use dynamic programming to solve this problem efficiently

• Create a 2D array to store if a subset with a particular sum exists

• Iterate through the array and update the 2D array accordingly

• Check if the value at the end of the iteration is true for the given K
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Q2. 
BFS Traversal in a Graph
Given an undirected and disconnected graph G(V, E) where V vertices are numbered from 0 to V-1, and E represents edges, your task is to output the BFS traversal starting from the ...read more
Ans. 
BFS traversal in a disconnected graph starting from vertex 0.
• Implement BFS algorithm to traverse the graph starting from vertex 0.

• Use a queue to keep track of visited nodes and their neighbors.

• Ensure to print the traversal sequence in the correct order.

• Handle disconnected components by checking for unvisited nodes.

• Follow the BFS approach of exploring neighbors before moving to the next level.
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Round duration - 60 minutes
Round difficulty - Easy

I told that my strength is problem solving and I can always find a way when there is a bottle-neck. Gave some examples of my experiences while doing my assignments.

Q1. 
Replace Spaces in a String
Given a string STR consisting of words separated by spaces, your task is to replace all spaces between words with the characters "@40".
Input:
The first line contains an integ...read more
Ans. 
Replace spaces in a string with '@40'.
• Iterate through each character in the string

• Replace spaces with '@40'

• Return the modified string
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Q1. Pl sql Unix api configuration
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Q2. Routing how to use proxy
Ans. 
Routing through a proxy involves configuring the proxy server to forward requests to the destination server.
• Configure the proxy server to listen for incoming requests

• Configure the proxy server to forward requests to the destination server

• Configure the client to use the proxy server for outgoing requests

• Use a proxy server to bypass network restrictions or improve performance

• Examples: Nginx, Apache, Squid
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Round duration - 70 minutes
Round difficulty - Medium

Timing: 6:00 pm
3 coding questions of medium to be solved in 70 minutes.

Q1. 
Maximum Subarray Sum Problem Statement
Given an array of numbers, the task is to find the maximum sum of any contiguous subarray of the array.
Input:
The first line of input contains the size of the arr...read more
Ans. 
Find the maximum sum of any contiguous subarray in an array of numbers in O(N) time.
• Use Kadane's algorithm to find the maximum subarray sum in O(N) time.

• Initialize two variables: maxEndingHere and maxSoFar to keep track of the maximum sum.

• Iterate through the array and update the variables accordingly.

• Return the maxSoFar as the result.
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Q2. 
Closest Leaf in a Binary Tree
Ninja is stuck in a maze represented as a binary tree, and he is at a specific node ‘X’. Help Ninja find the shortest path to the nearest leaf node, which is considered an ex...read more
Ans. 
Find the minimum distance from a given node to the nearest leaf node in a binary tree.
• Traverse the binary tree from the given node 'X' to find the nearest leaf node.

• Use a queue for level order traversal to efficiently find the nearest leaf node.

• Calculate the distance from node 'X' to each leaf node and return the minimum distance.
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Q3. 
Rotting Oranges Problem Statement
You are given a grid containing oranges where each cell of the grid can contain one of the three integer values:
• 0 - representing an empty cell
• 1 - representing a fre...read more
Ans. 
Find the minimum time required to rot all fresh oranges in a grid.
• Use Breadth First Search (BFS) to simulate the rotting process of oranges.

• Track the time taken to rot all fresh oranges and return the result.

• If any fresh oranges remain after simulation, return -1 as it is impossible to rot all oranges.
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Round duration - 45 minutes
Round difficulty - Medium

Timing: 2:00 pm
Online round over google meet, code at google docs.
The interviewer was friendly, encouraging, and humble.

Q1. 
Smallest Integer Not Representable as Subset Sum
Given a non-decreasing sorted array ARR of N positive numbers, determine the smallest positive integer that cannot be expressed as the sum of elements from...read more
Ans. 
The task is to find the smallest positive integer value that cannot be represented as a sum of elements of any proper subset of the given array.
• The array is sorted in non-decreasing order, so we can iterate through the array and keep track of the maximum sum we can form.

• If the current element is greater than the maximum sum + 1, then the maximum sum + 1 is the smallest positive integer that cannot be represented.

• If all...read more
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Round duration - 45 minutes
Round difficulty - Medium

Timing: 2:00 pm
Online round over google meet, code at google docs.
The interviewer was not speaking much. It was a bit strange.

Q1. 
Bottom Right View of Binary Tree Problem Statement
Your task is to identify and return the bottom right view of a given binary tree.
This involves viewing the binary tree from an angle of 45 degrees from...read more
Ans. 
Identify and return the bottom right view of a given binary tree by viewing it from an angle of 45 degrees from the bottom right side.
• Traverse the binary tree in a right-to-left manner and keep track of the last node encountered at each level.

• Use a queue for level order traversal and update the result array with the last node at each level.

• Return the result array sorted in ascending order as the bottom right view of th
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Round duration - 30 Minutes
Round difficulty - Easy

Timing: 7:00 pm
The interviewer was friendly and in a bit of a hurry.