public boolean separates(int a,int b){
  return A.get(a) && B.get(b) || A.get(b) && B.get(a);
}

public boolean separates ( int a , int b ) { return A . get ( a ) && B . get ( b ) || A . get ( b ) && B . get ( a ) ; }
returns true , if split separates taxa a and b
