PHP Trait Gliph\Graph\AdjacencyList

Adjacency lists store vertices directly, and edges relative to the vertices they connect. That means there is no overall list of edges in the graph; only a list of the graph's vertices. In this implementation, that list is keyed by vertex, with the value being a list of all the vertices to which that vertex is adjacent - hence, "adjacency list." Consequently, this structure offers highly efficient access to vertices, but less efficient access to edges. In an undirected graph, the edges are stored in both vertices' adjacency lists. In a directed graph, only the out-edges are stored in each vertex's adjacency list. This makes accessing in-edge information in a directed graph highly inefficient.

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Protected Properties

Property	Type	Description
$size	integer	We keep track because calculating it on demand is expensive.
$vertices	SplObjectStorage	Contains the adjacency list of vertices.
$walking	SplObjectStorage	Bookkeeper for nested iteration.

Public Methods

Method	Description
__construct ( )
ensureVertex ( $vertex )
hasVertex ( $vertex )
order ( )
size ( )
vertices ( )

Protected Methods

Method	Description
getTraversableSplos ( SplObjectStorage $splos ) : SplObjectStorage	Helper function to ensure SPLOS traversal pointer is not overridden.

Method Details

__construct() public method

public __construct ( )

ensureVertex() public method

public ensureVertex ( $vertex )

getTraversableSplos() protected method

This would otherwise occur if nested calls are made that traverse the same SPLOS. This keeps track of which SPLOSes are currently being traversed, and if it's in use, it returns a clone. It is incumbent on the calling code to release the semaphore directly by calling $this->walking->detach($splos) when the traversal in question is complete. (This is very important!)

protected getTraversableSplos ( SplObjectStorage $splos ) : SplObjectStorage
$splos	SplObjectStorage	The SPLOS to traverse.
return	SplObjectStorage	A SPLOS that is safe for traversal; may or may not be a clone of the original.

hasVertex() public method

public hasVertex ( $vertex )

order() public method

public order ( )

size() public method

public size ( )

vertices() public method

public vertices ( )

Property Details

$size protected_oe property

We keep track because calculating it on demand is expensive.

protected int $size
return	integer

$vertices protected_oe property

Contains the adjacency list of vertices.

protected SplObjectStorage $vertices
return	SplObjectStorage

$walking protected_oe property

Bookkeeper for nested iteration.

protected SplObjectStorage $walking
return	SplObjectStorage