SISCone's complexity is dominated by the search for stable cones. If N is the number of particles in the event and n the number of particles in a cone, the complexity goes like
N n log(n)
dominated by the ordering of the O(n) points in the vicinity of each particle.
Note: for the version of SISCone with progressive-removal, the stable-sone search has to be repeated O(N/n) times, yielding a O(N2log(n)) complexity.