 A multitree ( also called a strongly unambiguous graph or a mangrove ) is a directed graph in which there is at most one directed path ( in either direction ) between any two vertices ; equivalently , it is a DAG in which , for every vertex v , the subgraph reachable from v forms a tree . 
 A multitree ( also called a strongly unambiguous graph or a mangrove ) <a href='drop_aux' title='1'><mark>is</mark></a>a directed graph in which <a href='dey_it' title='2'><mark>there</mark></a> is at most one directed path ( in either direction ) between any two vertices ; equivalently , it is a DAG in which , for every vertex v , the subgraph reachable from v forms a tree . 
A multitree ( also called a strongly unambiguous graph or a mangrove ) a directed graph in which it is at most one directed path ( in either direction ) between any two vertices ; equivalently , it is a DAG in which , for every vertex v , the subgraph reachable from v forms a tree .