  The rigorous theoretical analysis of the algorithm for a subclass of QSAT,
i.e. (1, 2)-QSAT, has been proposed in the literature. (1, 2)-QSAT, first
introduced in SAT'08, can be seen as quantified extended 2-CNF formulas. Until
now, within our knowledge, there exists no algorithm presenting the worst upper
bound for (1, 2)-QSAT. Therefore in this paper, we present an exact algorithm
to solve (1, 2)-QSAT. By analyzing the algorithms, we obtain a worst-case upper
bound O(1.4142m), where m is the number of clauses.
