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OI-codes/S2OJ/1497/1497.cpp

72 lines
1.4 KiB
C++

#include <iostream>
#include <chrono>
#include <map>
#include <random>
#include <set>
#include <vector>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 1e6 + 5;
int n, m, a, b, ans;
unsigned long long sum[N];
std::vector<std::pair<int, unsigned long long>> g[N];
std::map<int, unsigned long long> map;
std::set<unsigned long long> set;
void dfs(int u, int f, unsigned long long s) {
sum[u] = sum[f] ^ s;
for (auto e : g[u]) {
int v = e.first;
unsigned long long w = e.second;
if (v == f) continue;
dfs(v, u, w);
}
}
signed main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
std::mt19937_64 rand(std::chrono::system_clock::now().time_since_epoch().count());
cin >> n >> m;
for (int i = 1; i < n; i++) {
int u, v, w;
cin >> u >> v >> w;
if (!map.count(w)) map[w] = rand();
set.insert(map[w]);
g[u].emplace_back(v, map[w]);
g[v].emplace_back(u, map[w]);
}
dfs(1, 0, 0);
cin >> a >> b;
while (m--) {
int x = a % n + 1,
y = b % n + 1;
unsigned long long s = sum[x] ^ sum[y];
if (s == 0 || set.count(s)) ans++;
a = static_cast<long long>(a) * 666073 % 1000000007;
b = static_cast<long long>(b) * 233 % 998244353;
}
cout << ans << endl;
return 0;
}