[bzoj 1954]Pku3764 The xor-longest Path

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Pku3764 The xor-longest Path

Time Limit: 1 Sec  Memory Limit: 64 MB
Submit: 839  Solved: 369
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Description

 给定一棵n个点的带权树，求树上最长的异或和路径

Input

The input contains several test cases. The first line of each test case contains an integer n(1<=n<=100000), The following n-1 lines each contains three integers u(0 <= u < n),v(0 <= v < n),w(0 <= w < 2^31), which means there is an edge between node u and v of length w.

Output

For each test case output the xor-length of the xor-longest path.

Sample Input

4
1 2 3
2 3 4
2 4 6

Sample Output

7

HINT

The xor-longest path is 1->2->3, which has length 7 (=3 ⊕ 4) 
注意：结点下标从1开始到N....

对于x，y之间的异或和，等于x到根节点的异或和 ^ y到根节点的异或和。

然后把它们丢到trie里，贪心就好。

代码待补