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Trees - Coggle Diagram
Trees
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A tree is a connected acyclic graph. A graph that has no cycles but is not necessarily connected is called a forest: each
of its connected components is a tree
Trees have several important properties other graphs do not have. In particular,
the number of edges in a tree is always one less than the number of its vertices
this property is necessary but not sufficient
for a graph to be a tree. However, for connected graphs it is sufficient and hence provides a convenient way of checking whether a connected graph has a
cycle.
Types of trees
Rooted trees
for every two vertices in a tree, there always exists exactly one simple path from one of these
vertices to the other. This property makes it possible to select an arbitrary vertex
in a free tree and consider it as the root of the so-called rooted tree
Aplications
describing
hierarchies, from file directories to organizational charts of enterprises
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For any vertex v in a tree T , all the vertices on the simple path from the root
to that vertex are called ancestors of v
The vertex itself is usually considered its
own ancestor; the set of ancestors that excludes the vertex itself is referred to as the set of proper ancestors
If (u, v) is the last edge of the simple path from the
root to vertex v (and u = v), u is said to be the parent of v and v is called a child of u; vertices that have the same parent are said to be siblings. A vertex with no
children is called a leaf ; a vertex with at least one child is called parental
All the vertices for which a vertex v is an ancestor are said to be descendants of v; the
proper descendants exclude the vertex v itself
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