I want to store co-ordinates of points in a multiset.I know that multiset stores them in sorted order but I want to specifically store them as (x1,x2 are x co-ordinates of 2 points) if x1>x2 then x2 should go before x1 and if they are equal then store them based on y co-ordinate. How can I do it ? By default this doesn't seem to be the criteria? What method can I use?
