Build a Comment Tree | Dataford Interview Questions

Build a comment tree out of a list of comment nodes where there is a link to a parent. The comments should come out like they would on Reddit where there are parent and child comments.

Asked in the phone screen stage. The input is a flat list of comments, each with an id, parent_id, and content. Return the same comments organized as a tree, where each node includes its content and an optional list of child comments.

Function

def build_comment_tree(comments):

Input

comments is a list of dictionaries with keys id, parent_id, and content.

Output

Return a list of root comment nodes, each with id, content, and children.

Constraints

1 <= comments.length <= 10^5
Each comment id is unique
parent_id is either null or the id of another comment in the list
The input contains no cycles
The relative order of siblings should match the input order

Function Signature

def build_comment_tree(comments):

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Problem