编程介的小学生 2019-04-29 16:56 采纳率: 20.5%
浏览 130

二差数的一个建立的过程的实现,怎么采用C语言的程序的编写的过程实现的呢

Problem Description
There are N vertices connected by N−1 edges, each edge has its own length.
The set { 1,2,3,…,N } contains a total of N! unique permutations, let’s say the i-th permutation is Pi and Pi,j is its j-th number.
For the i-th permutation, it can be a traverse sequence of the tree with N vertices, which means we can go from the Pi,1-th vertex to the Pi,2-th vertex by the shortest path, then go to the Pi,3-th vertex ( also by the shortest path ) , and so on. Finally we’ll reach the Pi,N-th vertex, let’s define the total distance of this route as D(Pi) , so please calculate the sum of D(Pi) for all N! permutations.

Input
There are 10 test cases at most.
The first line of each test case contains one integer N ( 1≤N≤105 ) .
For the next N−1 lines, each line contains three integer X, Y and L, which means there is an edge between X-th vertex and Y-th of length L ( 1≤X,Y≤N,1≤L≤109 ) .

Output
For each test case, print the answer module 109+7 in one line.

Sample Input
3
1 2 1
2 3 1
3
1 2 1
1 3 2

Sample Output
16
24

  • 写回答

0条回答 默认 最新

    报告相同问题?

    悬赏问题

    • ¥15 file converter 转换格式失败 报错 Error marking filters as finished,如何解决?
    • ¥15 ubuntu系统下挂载磁盘上执行./提示权限不够
    • ¥15 Arcgis相交分析无法绘制一个或多个图形
    • ¥15 关于#r语言#的问题:差异分析前数据准备,报错Error in data[, sampleName1] : subscript out of bounds请问怎么解决呀以下是全部代码:
    • ¥15 seatunnel-web使用SQL组件时候后台报错,无法找到表格
    • ¥15 fpga自动售货机数码管(相关搜索:数字时钟)
    • ¥15 用前端向数据库插入数据,通过debug发现数据能走到后端,但是放行之后就会提示错误
    • ¥30 3天&7天&&15天&销量如何统计同一行
    • ¥30 帮我写一段可以读取LD2450数据并计算距离的Arduino代码
    • ¥15 飞机曲面部件如机翼,壁板等具体的孔位模型