question: public List < Object > idsByDFSFinishTime ( boolean increasing ) { if ( ! initialized ) { throw new IllegalArgumentException ( ) ; } int len = vertexList . size ( ) ; Object [ ] r = new Object [ len ] ; for ( Iterator < Vertex > allV = vertexList . iterator ( ) ; allV . hasNext ( ) ; ) { Vertex vertex = allV . next ( ) ; int f = vertex . finishTime ; if ( increasing ) { r [ f - 1 ] = vertex . id ; } else { r [ len - f ] = vertex . id ; } } return Arrays . asList ( r ) ; }
target:  Returns the ids of the vertexes in this graph ordered by depth-first search finish time. The graph must be frozen.