Let F(G)and Ft(G)be the zero forcing number and the total forcing number of G,respectively.Davila(2020)studied the relationship between the zero forcing number and the total forcing number for a tree,and proved that for any tree T,Ft(T)≥F(T)+1 and characterized all trees T with Ft(T)=F(T)+1.Li and Jiang(2022)proved that for any uncyclic graph G,Ft(G)≥F(G),and characterized all unicycle graphs G satisfying Ft(G)=F(G).In this paper,all trees T with Ft(T)=F(T)+1 and all partial sun graphs G with Ft(G)=F(G)+1 are characterized respectively by determining all trees and unicycle graphs with the total forcing number 3.
关键词
零强迫数/全强迫数/树图/单圈图
Key words
zero forcing number/total forcing number/tree/unicycle graph