The most significant advantage of AAs represented by ADAPT-VQE is that the Ansätze is assembled iteratively. In each adaptive iteration of AA, an operator is chosen and appended into the Ansätze, so that the order of final Ansätze generated by AA is apposite. The well-ordered AA Ansätze should be more compact and more accurate than UCCSD in most cases. An AA iterates k times until the convergence of the energy, so that a final Ansätze is assembled with k operators like