1. A pattern layout creation method comprising: producing a graph in which patterns produced based on a pattern layout diagram are each regarded as nodes and nodes of patterns adjacent to each other at a first distance are connected with each other by an edge; classifying each of the patterns produced based on the pattern layout diagram into two types so that two patterns corresponding to the nodes at both ends of the edge are types different to each other; correcting a classification result by grouping the patterns produced based on the pattern layout diagram in each node cluster connected by the edge or each node cluster connected via the node by the edge, and by inverting each of types of the pattern belonging to a same group as that of one pattern, out of a pair of patterns that are classified into a same type and that belong to respectively different groups adjacent to each other at a second distance larger than the first distance; and creating the pattern layout diagram based on the corrected classification result.