The figure of graph on ex2. in the last mail was not good.
I want to correct it.
[false]
ex.2 a tree graph of 4 branches
._._|_._.
|
names of vertices
v_1
v_4 v_0 v_2
v_3
[corrected]
ex.2 a star graph of 4 edges
._._|_._.
|
names of vertices
v_1
v_4 v_0 v_2
v_3