Imagine you’re a superhero escaping a villain’s lair. As you move from perilous room to perilous room, the doors close immediately behind you, barring any return.

For this dramatic example, we need a *directed* graph, where edges restrict the direction of movement between vertices.

We can move from `spikes`

to `lasers`

, but not from `lasers`

to `spikes`

. This differs from earlier examples when every edge was bi-directional.

Note the path `spikes`

to `lasers`

to `piranhas`

to `spikes`

. This path is a *cycle*, because it ends on the vertex where it began: `spikes`

.

### Instructions

Consider a city with one-way streets, how would you model this with a directed graph?

What other cycles exist in this graph?