Push–relabel maximum flow algorithm: Difference between revisions

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::{{nowrap|''h''(''u'') ≤ ''h''(''v'') + 1&emsp;∀(''u'', ''v'') ∈ ''E<sub>f</sub>''}}
 
The heights of ''s'' and ''t'' are fixed at {{nowrap|{{!}}''V''{{!}}}} and 0, respectively. {{nowrap|''h''(''u'')}} is a lower bound of the unweighted distance from ''u'' to ''t'' in {{nowrap|''G<sub>f</sub>''}} if ''t'' is reachable from ''u''. If ''u'' has been disconnected from ''t'', then {{nowrap|''h''(''u'') − {{!}}''V''{{!}}}} is a lower bound of the unweighted distance from ''u'' to ''s''. As a result, if a valid height function exists, there are no ''s''-''t'' paths in {{nowrap|''G<sub>f</sub>''}} because no such paths can be longer than {{nowrap|({{!}}''V''{{!}} − 1)}}.
The heights of ''s'' and ''t'' are fixed at {{nowrap|{{!}}''V''{{!}}}} and 0, respectively.
 
The height of a vertex is a lower bound of its unweighted distance in the residual network to ''t'' or to ''s'' if it has been separated from ''t''. An edge {{nowrap|(''u'', ''v'') ∈ ''E<sub>f</sub>''}} is called ''admissible'' if {{nowrap|''h''(''u'') {{=}} ''h''(''v'') + 1}}. The network {{nowrap|''G̃<sub>f</sub>''(''V'', ''Ẽ<sub>f</sub>'')}} where {{nowrap|''Ẽ<sub>f</sub>'' {{=}} {(''u'', ''v'') {{!}} (''u'', ''v'') ∈ ''E<sub>f</sub>'' ∧ ''h''(''u'') {{=}} ''h''(''v'') + 1}}} is called the ''admissible network''. The admissible network is acyclic.
 
===Operations===