Build Coverability Tree from Petri net
[node_tree,id_parent_tran] = buildtree(forward,backward,new_node,id_parent,id_tran,node_tree,id_parent_tran)
This function is used to build Coverability Tree recursively. Parameter node_tree represents state in the Coverability Tree's node. Row size equal with number of place in Petri net. Column size same with number of node in coverability tree. Parameter id_parent_tran keeps parent and transition of every node in Coverability Tree. This matrix has two rows. The first row represents parent and the second row represents transition. Column size equal with number of node in Coverability Tree.
Parameter id_parent is indices of new_node's parent. This node represents initial state is become root. We know root does not have parent so we give 0 to this parameter. Parameter id_tran shows indices of transition. Remember we do not get initial state from firing transition so we do not need this at first. We give 0 to this parameter too.