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| #include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
const int N = 100010, M = 2 * N, K = 31 * N;
int n;
int h[N], e[M], w[M], ne[M], idx;
int son[K][2], cnt;
int d[N]; // f(a, b) = f(a, root) ^ f(b, root)
void add(int a, int b, int c) {
e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx++;
}
void insert(int x) {
int p = 0;
for (int i = 30; ~i; i--) {
int u = x >> i & 1;
if (!son[p][u]) son[p][u] = ++idx;
p = son[p][u];
}
}
int query(int x) {
int p = 0, res = 0;
for (int i = 30; ~i; i--) {
int u = x >> i & 1;
if (son[p][!u]) {
res += 1 << i;
p = son[p][!u];
}
else p = son[p][u];
}
return res;
}
void init() {
memset(h, -1, sizeof h);
memset(ne, 0, sizeof ne);
idx = cnt = 0;
memset(d, 0, sizeof d);
memset(son, 0, sizeof son);
}
void dfs(int u, int father, int sum) {
d[u] = sum;
for (int i = h[u]; ~i; i = ne[i]) {
int j = e[i];
if (j != father) dfs(j, u, sum ^ w[i]);
}
}
int main() {
while (cin >> n) {
init();
for (int i = 0; i < n - 1; i++) {
int a, b, c;
scanf("%d%d%d", &a, &b, &c);
add(a, b, c), add(b, a, c);
}
dfs(0, -1, 0);
for (int i = 0; i < n; i++) insert(d[i]);
int res = 0;
for (int i = 0; i < n; i++) res = max(res, query(d[i]));
cout << res << endl;
}
return 0;
}
|