COMPUTING THE UNION OF 3-COLORED TRIANGLES
Jean‐Daniel Boissonnat, Olivier Devillers, Franco P. Preparata · International Journal of Computational Geometry & Applications · 1991
Given is a set S of n points, each colored with one of k≥3 colours. We say that a triangle defined by three points of S is 3-colored if its vertices have distinct colours. We prove in this paper that the problem of constructing the boundary of the union T(S) of all such 3-colored triangles can be done in optimal O(n log n) time.