Covering rectilinear polygons by rectangles

Three approximation algorithms to cover a rectilinear polygon that is neither horizontally nor vertically convex by rectangles are developed. All three guarantee covers that have at most twice as many rectangles as in an optimal cover. One takes O(n log n) time, where n is the number of vertices in the rectilinear polygon. The other two take O(n²) and O(n⁴) time. Experimental results indicate that the algorithms with complexity O(n²) and O(n⁴) often obtain optimal or near-optimal covers