File System Collection

You need to build a statistics module for a file system that groups files into collections, with the option of defining a hierarchy among those collections. Every file has a name, a positive integer size, and can belong to zero or more collections. A file record is a comma-separated string with this structure: " , , , ,..." The collection ID list is optional. If a file isn’t part of any collection, the record contains only the first two fields (fileName and fileSize).…