Public Types | Public Member Functions

DynArcLookUp< GR > Class Template Reference

Detailed Description

template<typename GR>
class lemon::DynArcLookUp< GR >

Using this class, you can find an arc in a digraph from a given source to a given target in amortized time O(logd), where d is the out-degree of the source node.

It is possible to find all parallel arcs between two nodes with the operator() member.

This is a dynamic data structure. Consider to use ArcLookUp or AllArcLookUp if your digraph is not changed so frequently.

This class uses a self-adjusting binary search tree, the Splay tree of Sleator and Tarjan to guarantee the logarithmic amortized time bound for arc look-ups. This class also guarantees the optimal time bound in a constant factor for any distribution of queries.

Template Parameters:
GRThe type of the underlying digraph.
See also:

#include <lemon/core.h>

List of all members.

Public Types

typedef GR Digraph
 The Digraph type.

Public Member Functions

 DynArcLookUp (const Digraph &g)
Arc operator() (Node s, Node t, Arc p=INVALID) const
 Find an arc between two nodes.

Constructor & Destructor Documentation

DynArcLookUp ( const Digraph g) [inline]


It builds up the search database.

Member Function Documentation

Arc operator() ( Node  s,
Node  t,
Arc  p = INVALID 
) const [inline]

Find an arc between two nodes.

sThe source node.
tThe target node.
pThe previous arc between s and t. It it is INVALID or not given, the operator finds the first appropriate arc.
An arc from s to t after p or INVALID if there is no more.

For example, you can count the number of arcs from u to v in the following way.

       DynArcLookUp<ListDigraph> ae(g);
       int n = 0;
       for(Arc a = ae(u,v); a != INVALID; a = ae(u,v,a)) n++;

Finding the arcs take at most O(logd) amortized time, specifically, the time complexity of the lookups is equal to the optimal search tree implementation for the current query distribution in a constant factor.

This is a dynamic data structure, therefore the data structure is updated after each graph alteration. Thus although this data structure is theoretically faster than ArcLookUp and AllArcLookUp, it often provides worse performance than them.
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