﻿ N-B-U-T Online Judge :: [1636] XorAgain
• ### [1636] XorAgain

• 时间限制: 1000 ms　内存限制: 65535 K
• 问题描述
• There is a tree which contains n nodes, of course it has n - 1 edges, with weight.

Now the problem is, finding the number of (a, b) that the exclusive-xor sum of the edges between a to b is zero. Note that (a, b) is equal to (b, a).

Since the answer is very large, output it after module 1000, 000, 007.

• 输入
• Input starts with an integer T (T <= 10) denoting the number of test case.
For each case, first line contains n (1 <= n <= 50000) denoting the number of node, next n - 1 lines following, each line contains three
integers u, v and w (1 <= u, v <= n, 0 <= w <= 10000) which means there is an edge between u and v whose weight is w.
You can assume that the input data is valid.
• 输出
• For each case, output the answer after module 1000, 000, 007.
• 样例输入
• 1
5
1 2 3
1 3 3
2 4 4
3 5 4
• 样例输出
• 7
• 提示
• In the example, the seven pair nodes are (1, 1)、(2, 2) 、(3, 3)、 (4, 4) 、(5, 5)、 (2, 3) and (4, 5).

• 来源
• Alex@NBUT
• 操作
﻿