摘要：This problem is same as the previous one, but has larger constraints. It was a Sunday morning when the three friends Selena, Shiro and Katie decided t 阅读全文

摘要：There are n lines l1,l2,…,ln on the 2D-plane. Staring at these lines, Calabash is wondering how many pairs of (i,j) that 1≤i<j≤n and li,lj share at le 阅读全文