Decision Problems

To keep things simple, we will mainly concern ourselves with decision problems. These problems only require a single bit output: ``yes'' and ``no''.

• Is this directed graph acyclic?
• Is there a spanning tree of this undirected graph with total weight less than w?
• Does this bipartite graph have a perfect matching?
• Does the pattern p appear as a substring in text t?

Usually yes-or-no answers are enough for computing an optimal answer with only a polynomial slow down.