Reachability

In graph theory, reachability refers to the ability to get from one vertex to another within a graph. A vertex ${\displaystyle s}$ can reach a vertex ${\displaystyle t}$ (and ${\displaystyle t}$ is reachable from ${\displaystyle s}$) if there exists a sequence of adjacent vertices (i.e. a path) which starts with ${\displaystyle s}$ and ends with ${\displaystyle t}$.

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