Flatten Threaded Comments for Rendering | Dataford Interview Questions

Write a function to flatten a deeply nested dictionary representing a threaded comment structure into a flat list for rendering.

Each comment is a dictionary with id, body, and an optional replies list containing child comment dictionaries. Return a preorder list of dictionaries containing each comment's id, body, and nesting depth, without mutating the input. Preserve the order of replies.

Function

def flatten_comments(comment):

Constraints

The input is a dictionary containing string fields id and body.
replies is either absent or a list of valid comment dictionaries.
The total number of comments is at most 1,000.
The comment structure is a tree with no cycles.
The input must not be mutated.

Function Signature

def flatten_comments(comment):

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Problem