Find the shortest path from one starting node to all other nodes in a graph with positive edge weights.
Order tasks so that every task comes after its prerequisites, using a queue-based approach.
Check if you can finish all courses given their prerequisite requirements (no circular dependencies).
Count separate groups of connected land cells in a grid.
Make a complete copy of a graph where each node and its connections are duplicated.
Starting from a pixel, change its color and all connected same-color pixels to a new color (like the paint bucket tool).
Find an order to take all courses respecting prerequisites, or determine it's impossible.