Total File Size

DatadogEasy

A file system is modelled as a tree of entries. Each entry is a dictionary of one of two kinds:

a file: {"type": "file", "size": n}, where n is its size in bytes;
a directory: {"type": "dir", "children": [...]}, where children is a list of entries and may be empty.

A directory's children list may contain both files and other directories, nested to any depth. A directory has no size of its own. A file's size is its size field.

Part 1: Sum of file sizes

You are given an entry, a file or directory in the tree described above.

Return the total size in bytes of all files in entry and its descendants. A file's total is its own size. A directory's total is the sum of the sizes of all files anywhere beneath it, at any depth. An empty directory's total is 0.

Example 1
entry
{"type":"dir","children":[{"size":100,"type":"file"},{"size":200,"type":"file"}]}
Output
300
Why: The directory contains two files of 100 and 200 bytes and nothing else, so the total is 300.
Example 2
entry
{"size":500,"type":"file"}
Output
500
Why: A file has no children, so its total is just its own size.
Example 3
entry
{"type":"dir","children":[{"size":10,"type":"file"},{"type":"dir","children":[{"size":40,"type":"file"},{"type":"dir","children":[{"size":5,"type":"file"}]}]}]}
Output
55
Why: The top directory holds a file of 10 bytes and a nested directory. That nested directory holds a file of 40 bytes and a deeper directory holding a file of 5 bytes, so the total is 10 + 40 + 5 = 55.

Constraints

The tree rooted at entry has at least 1 and at most 10^5 entries
The nesting depth of entry is at most 500
For every file, 0 <= size <= 10^9
Every directory has a children list; a file has no children

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