question: public int edgeIndex ( TriangulationPoint p1 , TriangulationPoint p2 ) { if ( points [ 0 ] == p1 ) { if ( points [ 1 ] == p2 ) { return 2 ; } else if ( points [ 2 ] == p2 ) { return 1 ; } } else if ( points [ 1 ] == p1 ) { if ( points [ 2 ] == p2 ) { return 0 ; } else if ( points [ 0 ] == p2 ) { return 2 ; } } else if ( points [ 2 ] == p1 ) { if ( points [ 0 ] == p2 ) { return 1 ; } else if ( points [ 1 ] == p2 ) { return 0 ; } } return - 1 ; }
target:  Get the neighbor that share this edge