Two Dimensional Node Arrays ( node_matrix )

Definition

An instance M of the parameterized data type node_matrix<E> is a partial mapping from the set of node pairs V x V of a graph to the set of variables of data type E, called the element type of M. The domain I of M is called the index set of M. M is said to be valid for all node pairs in I. A node matrix can also be viewed as a node array with element type $node\_array\< E\>$
($node\_array\< node\_array\< E\> \ \>$
).

#include < LEDA/node _matrix.h >

Creation

node_matrix<E>	M	creates an instance M of type node_matrix<E> and initializes the index set of M to the empty set.
node_matrix<E>	M(graph G)	creates an instance M of type node_matrix<E> and initializes the index set to be the set of all node pairs of graph G, i.e., M is made valid for all pairs in V x V where V is the set of nodes currently contained in G.
node_matrix<E>	M(graph G, E x)	creates an instance M of type node_matrix<E> and initializes the index set of M to be the set of all node pairs of graph G, i.e., M is made valid for all pairs in V x V where V is the set of nodes currently contained in G. In addition, M(v, w) is initialized with x for all nodes v, w $\in$ V.

Operations

void	M.init(graph G)	sets the index set of M to V x V, where V is the set of all nodes of G.
void	M.init(graph G, E x)	sets the index set of M to V x V, where V is the set of all nodes of G and initializes M(v, w) to x for all v, w $\in$ V.
const node_array<E>&	M[node v]	returns the node_array M(v).
const E&	M(node v, node w)	returns the variable M(v, w). Precondition M must be valid for v and w.

Implementation

Node matrices for a graph G are implemented by vectors of node arrays and an internal numbering of the nodes of G. The access operation takes constant time, the init operation takes time O(n²), where n is the number of nodes currently contained in G. The space requirement is O(n²). Note that a node matrix is only valid for the nodes contained in G at the moment of the matrix declaration or initialization (init). Access operations for later added nodes are not allowed.