An initial layout of at least a portion of a given layer of an integrated circuit design is decomposed into multiple sub-layouts by splitting each of a plurality of shapes of the initial layout into multiple segments, constructing a constraint graph to represent relationships between the segments, reducing the constraint graph to a stitch graph, determining at least one cut line of the stitch graph, and generating a decomposed layout based on the determined cut line. The decomposed layout in an illustrative embodiment includes first and second sub-layouts comprising respective disjoint subsets of the segments, with each of the sub-layouts of the decomposed layout being associated with a different pattern mask of a double patterning lithography process. The layout decomposition process advantageously minimizes the number of stitches between the sub-layouts without introducing excessive computational complexity.