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 "false" if a file with that name already exists

• 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

• Returns the size of the file as a string

• Returns "" (empty string) if file doesn't exist

` 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", ""]

`

• Store file metadata (name, size)

• Validate operations (existence checks)

• Return results in specified format

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

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

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

• Sort results by:

• File size (descending)

• File name (alphabetically) for ties

• Returns "" if no matches found

` 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)"

`

• Efficient prefix and suffix matching

• Sort by size (descending), then name (ascending)

• Format output correctly with file names and sizes

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

• Adds a new user with specified storage capacity (in bytes)

• Returns "true" if successful

• Returns "false" if user already exists

• 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

• 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

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) ]

• Track ownership of files

• Enforce capacity limits

• Remove files intelligently when reducing capacity

Support compressing and decompressing files to save storage space.

• 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

• 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

• 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)

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" ]