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Flow Network

A digraph where edges have capacities and material "flows" from a source to a sink. Max-flow equals min-cut — the deepest duality in graph theory.

What to know

  • Residual graph tracks remaining capacity plus reverse "undo" edges.
  • Ford-Fulkerson repeatedly finds augmenting paths until none remain.
  • Many matching and scheduling problems reduce to max-flow.

In the wild: Traffic/pipeline capacity planning, image segmentation, sports elimination, project selection.

Algorithms to reach for

Edmonds-Karp (BFS Ford-Fulkerson)

O(V · E²)

Max flow with guaranteed termination

Dinic’s algorithm

O(V² · E)

Max flow on larger networks via level graphs