#1497. 树(tree)

https://sjzezoj.com/submission/55682

S2OJ/1497/1497.cpp

@@ -0,0 +1,71 @@
+#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;
+}