Design File System With Create, Get and Delete Path
Design an in-memory file system that stores a string value at each path. The file system must support creating paths, retrieving stored values, and deleting paths.
Path Rules
- A valid path contains one or more lowercase English letter components separated by
/.
- Every valid path starts with
/.
- Examples of valid paths are
/documents and /documents/images.
- Examples of invalid paths include
"", /, documents, /documents/, /documents//images, and /Documents.
- The parent of a top-level path such as
/documents is the root, which is considered to exist.
- The root is used only as the parent of top-level paths and cannot be created, retrieved, or deleted.
- The file system does not distinguish between files and folders. Any path may store a value and may also have child paths.
Methods
Constructor
FileSystem()
Initializes an empty file system.
Create Path
boolean createPath(String path, String value)
Creates path and associates value with it.
- Return
true when the path is created successfully.
- Return
false if path is invalid.
- Return
false if value is exactly "-1".
- Return
false if the path already exists.
- Return
false if the immediate parent path does not exist.
- Creating a path does not automatically create any missing parent paths.
Get Value
String get(String path)
Returns the string value associated with path.
- Return
"-1" if path is invalid.
- Return
"-1" if the path does not exist.
Delete Path
boolean deletePath(String path)
Deletes path from the file system.
- Return
true if the path exists and is deleted.
- Return
false if path is invalid.
- Return
false if the path does not exist.
- If the deleted path has child paths, delete all of its descendants.
- Deleting a path does not affect its parent or sibling paths.
Deterministic Behavior
- Each existing path stores exactly one string value.
- Creating an existing path does not replace its current value.
- After a path is deleted, it does not exist unless it is successfully created again.
- Deleting a path always deletes its complete subtree.
- All operations are processed in the order in which they are called.
Constraints
- At most
10,000 calls will be made to createPath, get, and deletePath combined.
- For every valid path,
2 ≤ path.length() ≤ 100.
1 ≤ value.length() ≤ 1,000- Every component of a valid path contains only lowercase English letters
a-z.
value may contain printable characters, but it must not be exactly equal to "-1".- The value
"-1" is reserved to indicate an invalid or nonexistent path.
Examples
Example 1
FileSystem fileSystem = new FileSystem();
fileSystem.createPath(path = "/projects", value = "active") returns true.
fileSystem.get(path = "/projects") returns "active".
The top-level path is created successfully, and its stored value can be retrieved.
Example 2
FileSystem fileSystem = new FileSystem();
fileSystem.createPath(path = "/users", value = "all-users") returns true.
fileSystem.createPath(path = "/users/admin", value = "administrator") returns true.
fileSystem.createPath(path = "/users/admin/settings", value = "enabled") returns true.
fileSystem.get(path = "/users/admin") returns "administrator".
Each nested path is created after its immediate parent exists.
Example 3
FileSystem fileSystem = new FileSystem();
fileSystem.createPath(path = "/music/rock", value = "songs") returns false.
fileSystem.get(path = "/music/rock") returns "-1".
The path cannot be created because its parent path /music does not exist.
Example 4
FileSystem fileSystem = new FileSystem();
fileSystem.createPath(path = "/store", value = "open") returns true.
fileSystem.createPath(path = "/store/orders", value = "pending") returns true.
fileSystem.createPath(path = "/store/orders/recent", value = "five") returns true.
fileSystem.deletePath(path = "/store/orders") returns true.
fileSystem.get(path = "/store/orders") returns "-1".
fileSystem.get(path = "/store/orders/recent") returns "-1".
fileSystem.get(path = "/store") returns "open".
Deleting /store/orders also deletes its descendants, while its parent remains unchanged.
Example 5
FileSystem fileSystem = new FileSystem();
fileSystem.createPath(path = "/logs", value = "first") returns true.
fileSystem.createPath(path = "/logs", value = "second") returns false.
fileSystem.get(path = "/logs") returns "first".
Creating an existing path fails and does not replace its stored value.
Example 6
FileSystem fileSystem = new FileSystem();
fileSystem.createPath(path = "/", value = "root-value") returns false.
fileSystem.get(path = "/") returns "-1".
fileSystem.deletePath(path = "/") returns false.
The root is not a valid path for creation, retrieval, or deletion.
Example 7
FileSystem fileSystem = new FileSystem();
fileSystem.createPath(path = "/reports/", value = "annual") returns false.
fileSystem.get(path = "/reports/") returns "-1".
fileSystem.deletePath(path = "reports") returns false.
The operations fail because the supplied paths are invalid.
Example 8
FileSystem fileSystem = new FileSystem();
fileSystem.createPath(path = "/archive", value = "-1") returns false.
fileSystem.get(path = "/archive") returns "-1".
The path is not created because "-1" is reserved for invalid or nonexistent paths.