The irregularity of two types of trees.

The irregularity of a graph G is defined as the sum of weights vertical bar d (u) - (v) vertical bar of all edges u v 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.