The diagram below shows the street map of a city. If three police officers are to be positioned at street corners so that any point on any street can be seen by at least one officer, what are the letter codes of these street corners?
I took combinations of all letters (positions) as 11C3 = 165; such as (A,B,C),(A,B,D),(A,B,E),...and I am trying each combination individually.
But, this method is too long & tedious. Is there a smarter way of solving this puzzle problem?