Height labels
Initial BFS from sink → heights. During flow, adjust like push-relabel.
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Gap heuristic
Track count of nodes at each height. When some height h has count 0, all nodes with height > h effectively disconnected — force to V.
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Current arc pointer
Each vertex has 'current arc' pointer. Avoids re-scanning already-explored edges.
Complexity
Same O(V²·E) worst case. Practical: fastest on many competitive problem instances.