1. A computer-implemented pattern layout creation method comprising: producing, by a computer, a graph comprising a plurality of patterns based on a first pattern layout diagram, wherein two patterns adjacent to each other at a distance within a first distance range are connected with each other by an edge; classifying, by a computer, each of the plurality of patterns into two types so that two patterns connected by an edge have types different from each other; grouping the patterns, by a computer, into a plurality of groups, wherein patterns in each of the groups are connected to each other via edges; determining, by a computer, a score for each of the groups, comprising: extracting first pairs of patterns, wherein the patterns in each of the first pairs: belong to two neighboring groups, respectively; are adjacent to each other at a distance within a second distance range; and have same type; extracting second pairs of patterns wherein the patterns in each of the second pairs: belong to two neighboring groups, respectively; are adjacent to each other at a distance within a second distance range; and have different types; and calculating the score for each of the groups by subtracting the number of patterns in the corresponding group that belong to one of the second pairs from the number of patterns in the corresponding group that belong to one of the first pairs, wherein distances in the second distance range are longer than distances in the first distance range; correcting, by a computer, a classification result by inverting the types of the patterns in the group having a highest score; and dividing, by a computer, the first pattern layout diagram into two second pattern layout diagrams based on the corrected classification result, wherein one of the two second pattern layout diagrams comprises patterns having the first type, and the other one of the two second pattern layout diagrams comprises patterns having the second type.