Netflix Interview Questions

Background: Netflix requires efficient data storage and retrieval for the vast number of media files. An in-memory file system can help model how files are organized and accessed without relying on a physical disk.
Problem statement: You need to implement a basic in-memory file system that supports the following operations:
1. mkdir(String path): Create a directory at the specified path.
2. addContentToFile(String filePath, String content): Create a file at the specified path and add the given content to it. If the file already exists, append the content.
3. readContentFromFile(String filePath): Read and return the content of the file at the given path. If the file does not exist, return an empty string.
Function/class signature:

• def mkdir(self, path: str) -> None:


• def addContentToFile(self, filePath: str, content: str) -> None:


• def readContentFromFile(self, filePath: str) -> str:

Example 1:
Input:
mkdir('/a')
addContentToFile('/a/b.txt', 'hello')
addContentToFile('/a/b.txt', ' world')
readContentFromFile('/a/b.txt')
Output:
'hello world'
Explanation: The file /a/b.txt is created and contains 'hello'. After appending ' world', it contains 'hello world'.
Example 2:
Input:
mkdir('/c/d')
readContentFromFile('/c/d/e.txt')
Output:
''
Explanation: The file /c/d/e.txt does not exist, hence it returns an empty string.
Constraints:

• Each path component (after splitting by '/') will be non-empty and contain only letters.


• Path will start with a '/'.


• Length of path will be at most 100 characters.


• The number of operations will be at most 10^4.

Background: Netflix handles a vast amount of data, and efficient data parsing is essential for performance in streaming applications. A common requirement is converting user input strings into integers safely and efficiently.
Problem statement: Implement a function my_atoi that converts a string s into an integer. The function should ignore leading whitespace and handle optional '+' or '-' signs. It should return the converted integer, and clamp the value within the limits of a 32-bit signed integer. If s is invalid, return 0.
Function/class signature:

• def my_atoi(s: str) -> int:

Example 1:

• Input: " -42"


• Output: -42


• Explanation: The leading spaces are ignored, and the negative sign is parsed correctly.

Example 2:

• Input: "4193 with words"


• Output: 4193


• Explanation: Only the leading numeric part is considered before the non-numeric characters appear.

Constraints:

• The input string consists of English letters (upper/lowercase), digits, and spaces.


• The conversion should respect 32-bit signed integer limits: [-2^31, 2^31 - 1].

Background: In a platform like Netflix, efficient data processing and manipulation are crucial for handling user input and search functionalities. This problem relates to parsing and converting user input strings into usable integer values, akin to handling identifiers or counts.
Problem statement: Write a function that converts a string s to an integer according to the rules of the ASCII values of characters. The function should ignore any leading whitespace, handle optional leading + or - signs, and should not overflow (return the maximum or minimum value for int). You may assume that the input will always be a valid integer format within the bounds of a 32-bit signed integer.Function/class signature:

• def myAtoi(s: str) -> int:

Example 1:

• Input: " -42"


• Output: -42


• Explanation: The whitespace is ignored, and the leading - indicates the number is negative.

Example 2:

• Input: "4193 with words"


• Output: 4193


• Explanation: The function parses the leading integer until it hits a non-digit character.

Constraints:

• 0 <= s.length <= 200


• The resulting integer should be within the range of a 32-bit signed integer: [-2^31, 2^31 - 1].


• The input string will only contain printable ASCII characters.

**

Background: Netflix requires efficient storage and management for user-generated content and temporary files in its platform. A well-defined in-memory file system allows quick access and manipulation of files without the need for disk IO, enhancing performance.
Requirements:
1. Implement mkdir(path: str) to create directories.
2. Implement addContentToFile(filePath: str, content: str) to add content to files, creating the file if it does not exist.
3. Implement readContentFromFile(filePath: str) -> str to read the content of a file.
4. Implement ls(path: str) -> List[str] to list files and directories in a given path in lexicographical order.
Class API:

• mkdir(path: str) -> None - Creates directories.


• addContentToFile(filePath: str, content: str) -> None - Adds content to a file.


• readContentFromFile(filePath: str) -> str - Returns the content of the specified file.


• ls(path: str) -> List[str] - Lists files/directories in the path.

Example 1:
Input:
mkdir('/a')
addContentToFile('/a/b.txt', 'hello')
addContentToFile('/a/b.txt', ' world')
readContentFromFile('/a/b.txt')
Output: 'hello world'
Explanation: The file /a/b.txt was created and content was added successfully, returning the correct concatenated string.
Example 2:
Input:
mkdir('/c/d')
ls('/c')
Output: ['d']
Explanation: The directory d exists under c, showing a correct list of directories.
Constraints:

• Max depth of directories: 10


• Max length of file path: 100


• Max content per file: 1024 characters

Background: Netflix operates with vast amounts of data and content that need efficient access and manipulation. An in-memory file system allows for fast temporary storage and rapid development of features. This system would simulate the behavior of a file system to manage content effectively.
Requirements:
1. Must support creating a directory structure with mkdir(path).
2. Must allow listing files in a directory with ls(path).
3. Must enable adding content to a file with addContentToFile(filePath, content).
4. Must allow reading the content of a file with readContentFromFile(filePath).
5. Handle non-existing paths gracefully.
Class API:

• def mkdir(path: str) -> None: Creates a new directory at the specified path.


• def ls(path: str) -> List[str]: Returns a list of files/directories in the specified path.


• def addContentToFile(filePath: str, content: str) -> None: Appends content to the specified file.


• def readContentFromFile(filePath: str) -> str: Returns the content of the specified file.

Example 1:
Input: mkdir('/a')
Output: None
Explanation: Creates directory /a.
Input: addContentToFile('/a/b.txt', 'hello')
Output: None
Explanation: Creates file /a/b.txt with content hello.
Input: ls('/a')
Output: ['b.txt']
Explanation: Lists files in directory /a.
Example 2:
Input: mkdir('/c/d/e')
Output: None
Explanation: Creating nested directories should work, thus /c/d/e is created from scratch.
Constraints:

• Maximum of 1000 directories and files.


• File names can be up to 100 characters long.


• Paths are guaranteed to be valid as per Unix file path rules.

Background: Netflix needs an in-memory file system to simulate and test features relevant to streaming and content storage without relying on disk I/O. This helps in optimizing performance and facilitating faster iterations during development.
Requirements:
1. Implement a method mkdir(path: str), which creates a directory at the specified path.
2. Implement a method ls(path: str) -> List[str], that lists all files and directories at the specified path in alphabetical order.
3. Implement a method addContentToFile(filePath: str, content: str), which adds content to a file; if the file does not exist, it should create it.
4. Implement a method readContentFromFile(filePath: str) -> str, which reads and returns the content of the specified file.
Class API:

• mkdir(path: str) -> None: Creates a directory at the specified path.


• ls(path: str) -> List[str]: Returns a list of the files and directories at the specified path.


• addContentToFile(filePath: str, content: str) -> None: Adds content to the file or creates it if it doesn’t exist.


• readContentFromFile(filePath: str) -> str: Reads the content of the specified file.

Example 1:
Input: mkdir('/a') → Output: None → Explanation: A directory /a is created.
Input: addContentToFile('/a/b.txt', 'hello') → Output: None → Explanation: A new file /a/b.txt is created with content 'hello'.
Input: readContentFromFile('/a/b.txt') → Output: 'hello' → Explanation: Content from the file is retrieved successfully.
Example 2:
Input: addContentToFile('/a/b.txt', ' world') → Output: None → Explanation: Content is appended to the file, now /a/b.txt contains 'hello world'.
Constraints:

• Up to 1000 directories or files can be created.


• Directory and file names will only contain lowercase letters or the special character, /.


• The file size will not exceed 1MB.


• All operations should be done in reasonable time (O(log n) for searches).

Background: Netflix aims to enhance user engagement through varied content formats, including literature. A digital library system can help users access books easily while keeping track of lending history. Requirements:
1. Must support adding, removing, and searching books by title or author.
2. Should allow users to check out and return books, updating the status accordingly.
3. Maintain a list of all borrowers and their borrowed books.
4. Implement a method to get the most borrowed books.
5. Ensure thread safety when multiple users access the library simultaneously.Class API:

• add_book(title: str, author: str) -> None: Adds a book to the library.


• remove_book(title: str) -> None: Removes a book from the library.


• checkout_book(title: str, user: str) -> bool: Checks out a book to a user.


• return_book(title: str, user: str) -> bool: Returns a book borrowed by a user.


• get_most_borrowed() -> List[str]: Returns a list of the most borrowed books.

Example 1:
Input:
add_book('1984', 'George Orwell')
checkout_book('1984', 'User1')
Output:
True
Explanation: Book '1984' is successfully checked out by 'User1'.Example 2:
Input:
return_book('1984', 'User1')
Output:
True
Explanation: Book '1984' is successfully returned by 'User1'.Constraints:

• Maximum of 10,000 books.


• Maximum of 1,000 concurrent users.


• Book titles must be unique within the library.