A9711 | Birthday
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内存限制256MB
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题目描述
Ali is Hamed's little brother and tomorrow is his birthday. Hamed wants his brother to earn his gift so he gave him a hard programming problem and told him if he can successfully solve it, he'll get him a brand new laptop. Ali is not yet a very talented programmer like Hamed and although he usually doesn't cheat but this time is an exception. It's about a brand new laptop. So he decided to secretly seek help from you. Please solve this problem for Ali.
An $n$ -vertex weighted rooted tree is given. Vertex number $1$ is a root of the tree. We define $d(u,v)$ as the sum of edges weights on the shortest path between vertices $u$ and $v$ . Specifically we define $d(u,u)=0$ . Also let's define $S(v)$ for each vertex $v$ as a set containing all vertices $u$ such that $d(1,u)=d(1,v)+d(v,u)$ . Function $f(u,v)$ is then defined using the following formula:
The goal is to calculate $f(u,v)$ for each of the $q$ given pair of vertices. As the answer can be rather large it's enough to print it modulo $10^{9}+7$ .
An $n$ -vertex weighted rooted tree is given. Vertex number $1$ is a root of the tree. We define $d(u,v)$ as the sum of edges weights on the shortest path between vertices $u$ and $v$ . Specifically we define $d(u,u)=0$ . Also let's define $S(v)$ for each vertex $v$ as a set containing all vertices $u$ such that $d(1,u)=d(1,v)+d(v,u)$ . Function $f(u,v)$ is then defined using the following formula:
The goal is to calculate $f(u,v)$ for each of the $q$ given pair of vertices. As the answer can be rather large it's enough to print it modulo $10^{9}+7$ .
输入格式
Ali is Hamed's little brother and tomorrow is his birthday. Hamed wants his brother to earn his gift so he gave him a hard programming problem and told him if he can successfully solve it, he'll get him a brand new laptop. Ali is not yet a very talented programmer like Hamed and although he usually doesn't cheat but this time is an exception. It's about a brand new laptop. So he decided to secretly seek help from you. Please solve this problem for Ali.
An $n$ -vertex weighted rooted tree is given. Vertex number $1$ is a root of the tree. We define $d(u,v)$ as the sum of edges weights on the shortest path between vertices $u$ and $v$ . Specifically we define $d(u,u)=0$ . Also let's define $S(v)$ for each vertex $v$ as a set containing all vertices $u$ such that $d(1,u)=d(1,v)+d(v,u)$ . Function $f(u,v)$ is then defined using the following formula:
The goal is to calculate $f(u,v)$ for each of the $q$ given pair of vertices. As the answer can be rather large it's enough to print it modulo $10^{9}+7$ .
An $n$ -vertex weighted rooted tree is given. Vertex number $1$ is a root of the tree. We define $d(u,v)$ as the sum of edges weights on the shortest path between vertices $u$ and $v$ . Specifically we define $d(u,u)=0$ . Also let's define $S(v)$ for each vertex $v$ as a set containing all vertices $u$ such that $d(1,u)=d(1,v)+d(v,u)$ . Function $f(u,v)$ is then defined using the following formula:
The goal is to calculate $f(u,v)$ for each of the $q$ given pair of vertices. As the answer can be rather large it's enough to print it modulo $10^{9}+7$ .
输出格式
Ali is Hamed's little brother and tomorrow is his birthday. Hamed wants his brother to earn his gift so he gave him a hard programming problem and told him if he can successfully solve it, he'll get him a brand new laptop. Ali is not yet a very talented programmer like Hamed and although he usually doesn't cheat but this time is an exception. It's about a brand new laptop. So he decided to secretly seek help from you. Please solve this problem for Ali.
An $n$ -vertex weighted rooted tree is given. Vertex number $1$ is a root of the tree. We define $d(u,v)$ as the sum of edges weights on the shortest path between vertices $u$ and $v$ . Specifically we define $d(u,u)=0$ . Also let's define $S(v)$ for each vertex $v$ as a set containing all vertices $u$ such that $d(1,u)=d(1,v)+d(v,u)$ . Function $f(u,v)$ is then defined using the following formula:
The goal is to calculate $f(u,v)$ for each of the $q$ given pair of vertices. As the answer can be rather large it's enough to print it modulo $10^{9}+7$ .
An $n$ -vertex weighted rooted tree is given. Vertex number $1$ is a root of the tree. We define $d(u,v)$ as the sum of edges weights on the shortest path between vertices $u$ and $v$ . Specifically we define $d(u,u)=0$ . Also let's define $S(v)$ for each vertex $v$ as a set containing all vertices $u$ such that $d(1,u)=d(1,v)+d(v,u)$ . Function $f(u,v)$ is then defined using the following formula:
The goal is to calculate $f(u,v)$ for each of the $q$ given pair of vertices. As the answer can be rather large it's enough to print it modulo $10^{9}+7$ .
输入输出样例
输入 #1
5 1 2 1 4 3 1 3 5 1 1 3 1 5 1 1 1 5 2 4 2 1 3 5
输出 #1
10 1000000005 1000000002 23 1000000002
输入 #2
8 1 2 100 1 3 20 2 4 2 2 5 1 3 6 1 3 7 2 6 8 5 6 1 8 2 3 5 8 2 6 4 7 6 1
输出 #2
999968753 49796 999961271 999991235 999958569 45130
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评测结果：Accepted