I. Introduction
DNA self-assembly is one of the most significant application and an important method of DNA computation. Winfree et al. first proposed the idea of computation by self-assembled DNA tiles [1]. The first experimental demonstrations of computing using DNA tile assembly was in [2]. Because of its practical importance, DNA self-assembly has received increased theoretical attention over the last few years. Till now, computational systems based on self-assembly have been demonstrated in both one-dimensional arrangements called “string tiles” [1], [3] and two-dimensional (2D) lattices of DNA [4]. For 2D self-assembly, Winfree has proposed the tile assembly model and demonstrated that it is Turing-universal [4]. In particular, some of the recent works had focused on the assembling of squares. Brun proposed and studied some systems that compute the sums and products of two numbers using the tile assembly model [5], and then used it to solve some fundamental problems such as SubsetSum [6], satisfiability [7]. Inspired by Brun, Zhang et al. showed how the tile assembly process can be used for subtraction and division [8], and Cui et al. used the tile assembly model to solve 0–1 knapsack problem [9], maximum clique problem [10].