BFS for System Dependency Graph

At Meta, services such as News Feed, Ads Delivery, and Graph API can depend on other internal systems. Given a directed graph of system dependencies and a starting system, implement breadth-first search (BFS) to return the order in which systems are discovered, grouped by dependency distance.

A directed edge A -> B means system A depends directly on system B. Starting from start, traverse all reachable systems using BFS. Return two results:

The flat BFS traversal order.
A list of levels, where each level contains systems at the same distance from start.

Input / Output

Input:
- graph: a dictionary mapping each system name (string) to a list of directly dependent systems (list of strings)
- start: a string representing the starting system
Output:
- A dictionary with keys:
  - order: list of strings in BFS visitation order
  - levels: list of lists of strings, grouped by BFS depth

A directed edge A -> B means system A depends directly on system B. Starting from start, traverse all reachable systems using BFS. Return two results:

The flat BFS traversal order.
A list of levels, where each level contains systems at the same distance from start.

Input / Output

Input:
- graph: a dictionary mapping each system name (string) to a list of directly dependent systems (list of strings)
- start: a string representing the starting system
Output:
- A dictionary with keys:
  - order: list of strings in BFS visitation order
  - levels: list of lists of strings, grouped by BFS depth

Problem

Input / Output

Constraints

Function Signature

BFS for System Dependency Graph

Problem

Input / Output

Constraints

Function Signature