Self-aligned double patterning is one of the most promising double patterning techniques for sub-20nm nodes. As in any multiple patterning techniques, layout decomposition is the most important problem. In SADP decomposition, overlay is among the most primary concerns. Most of the existing works target at minimizing the overall overlay, while others totally forbid the overlay. On the other hand, most of the works either rely on exponential time methods, or apply heuristic that cannot guarantee to find a solution. In this paper, we consider the SADP decomposition problem in row-based standard cell layout, where the overlay violations are minimized. Although SADP decomposition has been shown to be NP-hard in general, we showed that it can be solved in polynomial time when the layout is row-based standard cells. We propose a polynomial time optimal algorithm that finds a decomposition with minimum overlay violations. The efficiency of our method is further demonstrated by the experimental results.