The inverse problem for indices of molecular graphs
Lang Rong · Jisuanji yu yingyong huaxue · 2004
The inverse problem for Zagreb index of molecular graphs was discussed.We determine the natural numbers forwhich there are molecular graphs such that their index values equal to the numbers.Among all the molecular graphs with nvertices and edges,the sufficient and necessary condition for molecular graphs with minimum value of Zagreb index,andthe necessary condition for molecular graphs with the maximum value are gived.This can be used to improve the efficiencyof computer searching for the molecular graphs with given value of Zagreb index,which is very interested in combinatorialchemistry for searching of new drugs.A linear-time algorithm for computing the value of Hosoya index for trees is given.We also present a problem of NP-complete.