Breadth First Search Traversal

Given a graph with n vertices and edges, perform BFS starting from vertex start. Return the BFS traversal order.

Examples
Input: [4,[[0,1],[0,2],[1,2],[2,3]],0]
Output: [0,1,2,3]
Hints

Breadth First Search Traversal

Given a graph with n vertices and edges, perform BFS starting from vertex `start`. Return the BFS traversal order.