A tree is a connected simple graph with no simple cycles.
- In a tree, there is a unique simple path between any two of its vertices.
- If we add an edge to a tree, it creates a cycle.
- If we remove an edge from a tree, it becomes not connected.
graph G {
layout=neato
node[shape=point]
4--1,2,3,5
5--6,7,8
8--9,10,11
}