OJ Board

There are many problems that can be solved by this way, can someone give me some papers or hints about this tree?

TKS:)

I just give each char with a prim,eg: a(2) b(3) c(5)...
so you can change each string to a long long int ,and use % to check!
so without any cut you will get ac, and if you improve it, I think you will get a better time:)

But just in my alg, I first found the 45 degree points, and use floor and ceil to deal with them separately, so can you give me an example to show my fault , Tks:)

I change each circle to two rectangles, and use O(n*log(n)) to solve it, but I got wa , Could some one give me some special Input&Output?
TKS