Definition: A vertex v is reachable from another vertex u if there is a path of any length from u to v.

Also known as reachability.

See also sink, source, connected graph.

Note: Usually applied only to directed graphs, since any vertex in a connected, undirected graph is reachable from any other vertex.

Author: JM


Single-source and multiple-source reachability algorithms (Java) from Sedgewick and Wayne "Algorithms" 4th edition.
Go to the Dictionary of Algorithms and Data Structures home page.

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Entry modified 15 October 2021.
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Cite this as:
Jason McCabe, "reachable", in Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed. 15 October 2021. (accessed TODAY) Available from: