Topological Sort

What it is

Topological sort means finding a valid order for executing or listing items with dependencies.

If A depends on B, then B must come before A.

When to use it

It appears when the problem talks about:

• prerequisites
• build order
• dependency pipelines
• tasks that must happen before other tasks

Common mistake

The classic mistake is expecting a single unique order.

There are often many valid orders.

The point is respecting dependencies, not finding the prettiest sequence.

Better question

Before using it, ask:

1. is there a clear “must come before” relationship?
2. does the problem break if I swap some items?
3. can there be a cycle, and what would that mean here?