Practice/Anthropic/Cloud Storage System (Online Assessment)

Cloud Storage System (Online Assessment)

CodingMust

Problem Overview

You are implementing an in-memory cloud storage system that manages files and their metadata. The system does NOT interact with the real filesystem - all operations are simulated in memory.

This is a progressive online assessment (OA) with 4 levels that unlock sequentially. Design your data structures carefully to accommodate future requirements.

Level Summary

• Level 1: Basic file operations (add, copy, get size)
• Level 2: Find files by prefix and suffix patterns
• Level 3: Multi-user system with capacity limits per user
• Level 4: File compression and decompression

Input/Output Format

• Input: Array of queries, each query is an array of strings
• Output: Array of strings representing results for each query
• Each query calls exactly one operation

Important Notes

• This is an in-memory system - no actual file I/O
• File and directory names never collide (guaranteed by problem)
• Plan data structures to support all levels

Level 1: Basic Operations

The cloud storage system supports adding files, copying files, and querying file sizes.

Operations

ADD_FILE name size

• Adds a new file with specified name and size (in bytes)
• Returns "true" if successful
• Returns "false" if a file with that name already exists

COPY_FILE nameFrom nameTo

• Copies the file at nameFrom to nameTo

• Returns "true" if successful

• Returns "false" if:

  • nameFrom doesn't exist
  • nameTo already exists
  • nameFrom points to a directory

GET_FILE_SIZE name

• Returns the size of the file as a string
• Returns "" (empty string) if file doesn't exist

Example

` queries = [ ["ADD_FILE", "/dir1/dir2/file.txt", "10"], ["COPY_FILE", "/dir1/dir2/file.txt", "/dir1/file.txt"], ["GET_FILE_SIZE", "/dir1/file.txt"], ["GET_FILE_SIZE", "/not-existing.file"] ]

Results: ["true", "true", "10", ""]

`

Requirements

• Store file metadata (name, size)
• Validate operations (existence checks)
• Return results in specified format

Level 2: Finding Files by Prefix and Suffix

Implement search functionality to find files matching prefix and suffix patterns.

New Operation

FIND_FILE prefix suffix

• Searches for files with names starting with prefix and ending with suffix

• Returns formatted string: "name1(size1), name2(size2), ..."

• Sort results by:

  1. File size (descending)
  2. File name (alphabetically) for ties

• Returns "" if no matches found

Example

` queries = [ ["ADD_FILE", "/root/dir/another_dir/file.mp3", "10"], ["ADD_FILE", "/root/file.mp3", "5"], ["ADD_FILE", "/root/music/file.mp3", "7"], ["FIND_FILE", "/root", ".mp3"] ]

Result: "/root/dir/another_dir/file.mp3(10), /root/music/file.mp3(7), /root/file.mp3(5)"

`

Requirements

• Efficient prefix and suffix matching
• Sort by size (descending), then name (ascending)
• Format output correctly with file names and sizes

Level 3: User Capacity Limits

Add multi-user support where each user has a storage capacity limit.

New Operations

ADD_USER userId capacity

• Adds a new user with specified storage capacity (in bytes)
• Returns "true" if successful
• Returns "false" if user already exists

ADD_FILE_BY userId name size

• Adds a file owned by the specified user

• Returns remaining capacity as string if successful

• Returns "" if:

  • User doesn't exist
  • File already exists
  • Adding file would exceed user's capacity

UPDATE_CAPACITY userId capacity

• Updates user's storage capacity limit
• If new capacity is less than current usage, removes largest files (alphabetically on tie) until under limit
• Returns number of removed files as string
• Returns "" if user doesn't exist

Special Cases

• User "admin" has unlimited capacity (for backward compatibility with Level 1 operations)
• COPY_FILE preserves the original file's owner
• If copying would exceed capacity, operation fails

Example

queries = [ ["ADD_USER", "user1", "125"], ["ADD_FILE_BY", "user1", "/dir/file.big", "50"], # Returns "75" ["ADD_FILE_BY", "user1", "/file.med", "30"], # Returns "45" ["UPDATE_CAPACITY", "user1", "50"], # Returns "2" (removes 2 files) ]

Requirements

• Track ownership of files
• Enforce capacity limits
• Remove files intelligently when reducing capacity

Level 4: File Compression

Support compressing and decompressing files to save storage space.

New Operations

COMPRESS_FILE userId name

• Compresses file if it belongs to the specified user

• Creates new file named name.COMPRESSED with size = original size / 2

• Original file is deleted

• Returns remaining capacity as string if successful

• Returns "" if:

  • User doesn't exist
  • File doesn't exist or doesn't belong to user
  • File already ends with .COMPRESSED

DECOMPRESS_FILE userId name

• Decompresses file (must end with .COMPRESSED)

• Restores original size (doubles the current size)

• Removes .COMPRESSED suffix

• Returns remaining capacity as string if successful

• Returns "" if:

  • User doesn't exist
  • File doesn't exist or doesn't belong to user
  • Decompression would exceed user's capacity
  • Decompressed version already exists

Important Notes

• All file sizes are guaranteed to be even (no fractional calculations)
• Compressed files cannot be compressed again
• COPY_FILE preserves the .COMPRESSED suffix
• File names can only contain lowercase letters (so .COMPRESSED can only come from compression)

Example

queries = [ ["ADD_USER", "user1", "1000"], ["ADD_FILE_BY", "user1", "/dir/file.mp4", "500"], ["COMPRESS_FILE", "user1", "/dir/file.mp4"], # Returns "750" ["GET_FILE_SIZE", "/dir/file.mp4.COMPRESSED"], # Returns "250" ["GET_FILE_SIZE", "/dir/file.mp4"], # Returns "" (file removed) ["DECOMPRESS_FILE", "user1", "/dir/file.mp4.COMPRESSED"] # Returns "500" ]