Not all digraphs that look like directed trees are directed trees. For example the drawing in Fig 2.1b is not a directed tree because node 2 is the head of two arcs (two arrows point to node 2) It also has two"roots", node 1 and node 5.
Not all digraphs that look like directed trees are directed trees. For example the drawing in Fig 2.1b is not a directed tree because node 2 is the head of two arcs (two arrows point to node 2) It also has two"roots", node 1 and node 5.
The drawing in Fig 2.1c is not a directed tree, because there is no root, a node which has no arrow pointing at it.
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