Property information
x surrounded_by y if and only if (1) x is adjacent to y and for every region r that is adjacent to x, r overlaps y (2) the shared boundary between x and y occupies the majority of the outermost boundary of x
x surrounded_by y if and only if (1) x is adjacent to y and for every region r that is adjacent to x, r overlaps y (2) the shared boundary between x and y occupies the majority of the outermost boundary of x