Breadth First Search

Note

Use queue<T> to store the nodes in Breadth-first order.

To avoid visiting the same node twice, use a vector<bool> or unordered_set<T> to store whether the node has been visited.

Make sure marking the node as visited before the node is enqueued! Otherwise the same node might be added multiple times.

Problems

• 1311. Get Watched Videos by Your Friends (Medium)