Examples overlapping case. We divide the overlapping region into four sub-regions equally first. ${\rm{C_{E1}}}$ and ${\rm{C_{E2}}}$ are the center positions of example 1 and 2, respectively. CSR1–CSR4 are the center positions of sub-regions. For the sub-region 1 in the upper left part, CSR1, the distance $|{\rm{C_{SR1}}}-{\rm{C_{E1}}}|$ is smaller than $|{\rm{C_{SR1}}}-{\rm{C_{E2}}}|$. Therefore we consider example 1 to override sub-region 1. We use the same strategy to deal with the other sub-regions.