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A graph is a mathematical structure indicated with the tuple (V,E) where V indicates nodes and E indicates the arcs.
A graph can be ordered or non-ordered.
When the arc enter in the node it is called “incoming” arc meanwhile the arc exit from the node it is called “outgoing” arc.
When two nodes are connected by an arc they are adjacent and the arc is incident on these.
The degree of a node is the number of adjacent nodes that it has.
in “example 1” all nodes has degree 1 meanwhile in “example 2”, node “4” has degree 2, node “2” has degree 3….