EBAD's blog

By EBAD, history, 3 weeks ago, In English,

You're given a tree with n vertices.Your task is to calculate number of ways to give the ith edge of tree an integer number from interval [li,ri] such that sum of the numbers of all paths do not exceed k.output answer modulo 1e9+7.1<=li<=ri<=1e5 1<=n,k<=1e5 I really have no idea to solve this, please help me.