### The irregularity of two types of trees

*Li Jianxi, Yang Liu, Wai Chee Shiu*

#### Abstract

The irregularity of a graph G is defined as the sum of
weights |d(u)-d(v)| of all edges uv of
G, where d(u) and d(v) are the
degrees of the vertices u and v in
G, respectively. In this paper, some structural
properties on trees with maximum (or minimum) irregularity among trees
with given degree sequence and trees with given branching number are
explored, respectively. Moreover, the corresponding trees with maximum
(or minimum) irregularity are also found, respectively.

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