/**
* Does the mapping respected the component grouping specified by the query.
*
* @param mapping a permutation of the query vertices
* @return the mapping preserves the specified grouping
*/
@Override
public boolean apply(final int[] mapping) {
// no grouping required
if (queryComponents == null) return true;
// bidirectional map of query/target components, last index
// of query components holds the count
int[] usedBy = new int[cc.nComponents() + 1];
int[] usedIn = new int[queryComponents[mapping.length] + 1];
// verify we don't have any collisions
for (int v = 0; v < mapping.length; v++) {
if (queryComponents[v] == 0) continue;
int w = mapping[v];
int queryComponent = queryComponents[v];
int targetComponent = targetComponents[w];
// is the target component already used by a query component?
if (usedBy[targetComponent] == 0) usedBy[targetComponent] = queryComponent;
else if (usedBy[targetComponent] != queryComponent) return false;
// is the query component already used in a target component?
if (usedIn[queryComponent] == 0) usedIn[queryComponent] = targetComponent;
else if (usedIn[queryComponent] != targetComponent) return false;
}
return true;
}
/**
* Create a predicate to match components for the provided query (grouping) and target (connected
* components).
*
* @param grouping query grouping
* @param cc connected component of the target
*/
public ComponentGrouping(int[] grouping, ConnectedComponents cc) {
this.queryComponents = grouping;
this.cc = cc;
this.targetComponents = cc != null ? cc.components() : null;
}