What is Multi-Source BFS?

A technique where multiple starting nodes are added to the queue initially, allowing the "wavefront" to expand from several points at once (e.g., Rotting Oranges).

How do I handle cycles in graph BFS?

Use a "visited" set to keep track of nodes already processed and avoid infinite loops.

Breadth-First Search

Easy

BFS Fundamentals & Patterns

Mastering the Queue traversal patterns.

10 min

Solve on LeetCode

Standard BFS vs Level-Order BFS

There are two main ways to write the BFS loop. Understanding the distinction is key for solving different types of problems.

Trees vs Graphs

Trees:

No cycles.
Usually directed (Parent -> Child).
No visited set needed (unless traversing up to parents).

Graphs:

Can have cycles (A -> B -> A).
Can be undirected.
MUST use visited set to prevent infinite loops.

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