100+ Software Development Engineer II Interview Questions and Answers

Calculate sum of large numeric comma separated strings without converting to integers.

• Split the strings by comma to get individual numbers

• Iterate from right to left and add digits, carrying over if necessary

• Maintain correct position of commas in the output string

I own 5 microservices that handle traffic at a scale of 10,000 requests per minute.

• I own 5 microservices

• They handle traffic at a scale of 10,000 requests per minute

Given an array, find a subset that sums to a given sum K and print all triplets that sum to K.

• Use a recursive approach to find subsets that sum to K

• Use a nested loop to find triplets that sum to K

• Avoid using duplicate elements in triplets

Design a portfolio management system to add and sell stocks, calculate returns, and display current prices and returns.

• Create a class for the portfolio with methods to add and sell stocks

• Implement a method to calculate the percentage return on the portfolio

• Maintain a list of stocks in the portfolio with their current prices and returns

• Use arrays or lists to store the portfolio data

• Ensure proper error handling for invalid inputs or insufficient data

Find a missing number in an unsorted array with elements in the range [1,n].

• Use a hash set to store the elements and check for missing numbers.

• Calculate the sum of all elements and subtract it from the sum of the range [1,n].

• Use XOR operation to find the missing number.

Use channels in Go to sync two goroutines passing data between them.

• Create a channel to pass data between the goroutines

• Use a select statement to wait for data to be passed

• Ensure proper synchronization to avoid race conditions

Calculate top 20 percentile of student details based on score in a student table.

• Calculate the 80th percentile score using formula: 80th_percentile = 0.8 * total_students

• Sort the scores in descending order and find the score at 80th percentile position

• Retrieve student details with scores greater than or equal to the 80th percentile score

Design a database structure for an e-commerce service to showcase ordered products.

• Create a 'products' table with columns like product_id, name, price, etc.

• Create an 'orders' table with columns like order_id, customer_id, order_date, etc.

• Create a 'order_details' table to link products with orders, with columns like order_id, product_id, quantity, etc.

• Use foreign keys to establish relationships between tables.

• Consider indexing columns for faster retrieval of data.

To handle concurrent editing in Google Sheets, use operational transformation to synchronize changes and resolve conflicts.

• Implement operational transformation to track and merge concurrent edits

• Use version control to manage different versions of the sheet

• Apply locking mechanisms to prevent conflicts during editing

• Utilize real-time collaboration features to notify users of changes

• Implement conflict resolution strategies, such as last writer wins or manual resolution

A hashmap is a data structure that stores key-value pairs and allows for constant time lookup and insertion.

• Hashmaps use a hash function to map keys to indices in an array.

• Collisions can occur when multiple keys hash to the same index, which can be resolved using techniques like chaining or open addressing.

• Example: HashMap map = new HashMap<>(); map.put("key", 123); int value = map.get("key");

Implement a simplified Video Codex using data structures

• Use a hash table to store key-value pairs of video frames and their corresponding codecs

• Implement a priority queue to efficiently retrieve the most frequently accessed video frames

• Consider using a linked list to maintain the order of video frames in the codex

Create a console application to show flights between two cities in min no of hops

• Use graph traversal algorithms like BFS to find the shortest path between two cities

• Represent cities and flights as nodes and edges in a graph data structure

• Implement a console interface for users to input two cities and display the shortest path between them

Find the maximum distance between any two leaf nodes of a binary tree.

• Traverse the tree to find the maximum depth of left and right subtrees

• Calculate the maximum distance by adding the depths of left and right subtrees

Views are virtual tables that simplify complex queries. Indexes can be created on views to improve performance.

• Views are virtual tables created by querying one or more tables.

• They simplify complex queries by storing the query logic in the view.

• Indexes can be created on views to improve query performance.

• Indexes on views can speed up data retrieval by allowing the database to quickly locate the relevant data.

Count occurrences of given element in a sorted array.

• Use binary search to find the first and last occurrence of the element.

• Subtract the indices to get the count of occurrences.

• Handle edge cases like element not present in array.

Horizontal scaling is adding more machines to your pool of resources, while vertical scaling is adding more power (CPU, RAM) to an existing machine.

• Use horizontal scaling when you need to increase capacity by adding more machines to distribute the load.

• Use vertical scaling when you need to handle increased load on a single machine by adding more resources like CPU or RAM.

• Horizontal scaling is more cost-effective and provides better fault tolerance.

• Vertical scaling is easier t...read more

Plan ETL for various data sources by identifying sources, defining data extraction methods, transforming data, and loading into target systems.

• Identify all data sources and understand their structure and format

• Define data extraction methods based on the source systems (e.g. APIs, databases, files)

• Transform data as needed to match the target system's schema and requirements

• Consider data quality issues and implement data cleansing processes

• Load the transformed data into the tar...read more

Find the maximum length of a subarray with almost 2 distinct elements.

• Use a sliding window approach to keep track of the count of distinct elements in the subarray.

• Update the window size based on the number of distinct elements in the subarray.

• Keep track of the maximum length encountered so far.

Libraries provide pre-written code for common tasks, while polyfills fill in missing browser functionality.

• Libraries save time by providing pre-written code for common tasks

• Polyfills fill in missing browser functionality for older browsers

• Libraries can improve code readability and maintainability

• Polyfills can help ensure consistent behavior across different browsers

• Using libraries and polyfills can help developers focus on higher-level logic rather than low-level implementati...read more

Design SkipTracker() for Amazon Prime Music

• SkipTracker() should keep track of skipped songs in Amazon Prime Music

• It should maintain a list of skipped songs as an array of strings

• The list should be updated whenever a song is skipped

• SkipTracker() should provide methods to add, remove, and retrieve skipped songs

Clustered index physically reorders the data in the table, unclustered index does not, unique index enforces uniqueness of values.

• Clustered index physically reorders the data in the table based on the index key. Only one clustered index per table.

• Unclustered index does not reorder the data in the table. Can have multiple unclustered indexes per table.

• Unique index enforces uniqueness of values in the indexed column(s). Can be clustered or unclustered.

Design a chat room system where users can chat with each other and join chat rooms.

• Implement user authentication and authorization to ensure secure access to chat rooms.

• Create a database to store chat messages, user information, and chat room details.

• Develop a real-time messaging system using websockets for instant communication.

• Allow users to create new chat rooms and join existing ones.

• Include features like message history, notifications, and user profiles.

The interview consists of four back-to-back 1 hour sessions with 1 hour lunch break, including system design with the manager and LC medium-hard questions with the rest of the interviewers.

• Prepare for system design questions with the manager by understanding scalability, reliability, and performance considerations.

• Practice solving LC medium-hard questions to showcase problem-solving skills and algorithmic knowledge.

• Take advantage of the lunch break to relax and recharge for t...read more

Temp table is local to a session, global table is accessible across sessions, variable table is a table variable declared in a function or stored procedure.

• Temp table is created and dropped automatically when the session ends.

• Global table is created using a double hash (##) prefix and is accessible across sessions.

• Variable table is a table variable declared in a function or stored procedure and is only accessible within that scope.

Decode a string by expanding integers to repeat characters within brackets.

• Iterate through the string character by character

• If a digit is encountered, keep track of the number

• When encountering '[', push the current result and number onto the stack

• When encountering ']', repeat the substring inside brackets based on the number on top of the stack

• Continue until the entire string is decoded

Given a number x, find the minimum number of operations (decrement by 1 or multiply by 2) to convert it to y.

• Use a breadth-first search (BFS) approach to explore all possible operations and find the minimum number of steps.

• Start with x and generate all possible next numbers by decrementing or multiplying by 2.

• Keep track of the number of steps taken to reach each number and stop when y is found.

• Use a queue to implement the BFS algorithm.

• Example: x = 10, y = 30. Possible steps:...read more

Streams in Java8 offer concise and readable code for processing collections compared to traditional for loops.

• Streams provide functional-style operations like map, filter, and reduce for easy data processing.

• Streams allow for parallel processing of data, potentially improving performance.

• Streams promote immutability and encourage writing more declarative code.

• Streams reduce boilerplate code and make the code more readable and maintainable.

• Example: Using streams to filter a li...read more

Interface is a contract with no implementation, while abstract class can have some implementation.

• Interface can only have abstract methods, while abstract class can have both abstract and non-abstract methods.

• A class can implement multiple interfaces but can inherit only one abstract class.

• Interfaces are used to achieve multiple inheritance in Java.

• Abstract classes can have constructors, while interfaces cannot.

• Example: Interface - Runnable, Abstract class - Animal with abstr...read more

Given a binary tree, find the path with the largest sum of node values.

• Use depth-first search to traverse the tree and keep track of the current path sum.

• At each node, compare the current path sum with the maximum path sum seen so far.

• Return the path with the maximum sum.

• If the tree is empty, return an empty path.

Implement an in-memory backend for a social media app in 90 mins

• Use a HashMap to store user profiles and posts

• Implement methods for CRUD operations on user profiles and posts

• Consider implementing data structures like LinkedList or PriorityQueue for managing posts in chronological order

Implement merge sort algorithm to sort array of strings based on a given key

• Divide the array into two halves recursively

• Merge the two sorted halves based on the given key

• Repeat until the entire array is sorted

• Example: ['apple', 'banana', 'cherry'] sorted based on length: ['apple', 'cherry', 'banana']

Implement binary search to find the number in a sorted array with lowest code complexity.

• Use binary search algorithm to efficiently find the number in the sorted array.

• Compare the target number with the middle element of the array and adjust the search range accordingly.

• Repeat the process until the target number is found or the search range is exhausted.

Find max length of substring with equal 1s and 0s in a binary string.

• Use a hash table to store the difference between the count of 1s and 0s seen so far.

• If the difference is 0, update the max length seen so far.

• If the difference is already in the hash table, update the max length using the current index and the index where the difference was first seen.

• Return the max length.

• Example: '1100010110' -> 8

Determining job scheduling order based on dependencies

• Create a directed graph with jobs as nodes and dependencies as edges

• Use topological sorting to determine the order of scheduling

• If there is a cycle in the graph, it is not possible to schedule the jobs

• Consider using depth-first search to traverse the graph

Reverse a linked list and find number of characters in a string.

• To reverse a linked list, we can iterate through the list and change the pointers to reverse the order.

• To find the number of characters in a string, we can use the length property or iterate through the string and count the characters.

• For example, to reverse a linked list:

• Node* prev = NULL; Node* current = head; Node* next = NULL; while (current != NULL) { next = current->next; current->next = prev; prev = curre...read more

Implement timer in React using useTimeout and disable it after unmounting

• Use useState to store the timer ID

• Use useEffect to start the timer on component mount and clear it on unmount

• Use clearTimeout to disable the timer when the component unmounts

Designing classes and database for a product

• Identify the entities and relationships in the system

• Create a class diagram with attributes and methods

• Design the database schema with tables and relationships

• Consider performance, scalability, and security

• Use appropriate design patterns and principles

Remove the given node from the middle of a Linked List.

• Use two pointers, one moving at double the speed of the other to find the middle node.

• Update the pointers to remove the middle node by skipping it in the list.

Find the first k most occurring strings from a given list

• Use a hashmap to store the frequency of each string

• Sort the hashmap based on frequency in descending order

• Return the first k keys from the sorted hashmap

Create basic routes and schema diagram for specific requirements.

• Identify the specific requirements for the routes and schema

• Design the routes based on the HTTP methods (GET, POST, PUT, DELETE)

• Create the necessary endpoints and handlers for each route

• Define the schema for the data to be used in the routes

• Create a diagram to visualize the relationships between the schema entities

Search for a string efficiently in a character matrix.

• Use depth-first search (DFS) or breadth-first search (BFS) to traverse the matrix and search for the string.

• Optimize by pruning search paths if a mismatch is encountered.

• Consider using a Trie data structure for faster string matching.

• Handle edge cases like empty matrix or string, out of bounds indices, etc.

Implement a Sudoku solver and find the repetitive element in a list.

• For the Sudoku solver, implement a backtracking algorithm to fill in the empty cells while ensuring each row, column, and 3x3 subgrid contains unique numbers.

• For finding the repetitive element in a list, iterate through the list and keep track of the frequency of each element using a hashmap. Return the element with frequency greater than 1.

• Example for Sudoku solver: [[5,3,0,0,7,0,0,0,0],[6,0,0,1,9,5,0,0,0],....read more

Use a hierarchical query to find the number of employees under each manager.

• Use a recursive query to traverse the organizational hierarchy

• Count the number of employees under each manager

• Group the results by manager

HashSet is implemented using a hash table. Elements are not sorted in a HashSet.

• HashSet is implemented using a hash table data structure.

• Elements in a HashSet are not sorted, as they are stored based on their hash code.

• To sort elements in a HashSet, you can convert it to a List and then sort the List.

Detect cycle in a linked list and sorting algorithms

• To detect a cycle in a linked list, you can use Floyd's Tortoise and Hare algorithm

• Common sorting algorithms include Bubble Sort, Selection Sort, Insertion Sort, Merge Sort, Quick Sort, etc.

Different states in Activity lifecycle include onCreate, onStart, onResume, onPause, onStop, onDestroy.

• onCreate - Activity is being created

• onStart - Activity is becoming visible to the user

• onResume - Activity is in the foreground and has focus

• onPause - Activity is partially visible but still running

• onStop - Activity is no longer visible to the user

• onDestroy - Activity is being destroyed

CDC stands for Change Data Capture in SQL Server.

• CDC is a feature in SQL Server that captures changes made to data in a table.

• It allows you to track insert, update, and delete operations on the table.

• CDC uses a separate table to store the changes made to the tracked table.

• It is useful for auditing, data replication, and data warehousing purposes.