L - Listing Tedious Paths

https://codeforces.com/gym/103960/submission/179151562

Gym/103960/L/L.cpp

@@ -0,0 +1,102 @@
+#include <iostream>
+#include <numeric>
+#include <utility>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e5 + 5;
+
+int n, c[N], fa[N], siz[N], son[N], cnt[N], color[N];
+long long ans[N], res;
+std::vector<int> g[N];
+std::vector<std::pair<int, int>> edges;
+
+void add(int u) {
+    res += color[c[u]] - 2 * cnt[c[u]]++ - 1;
+}
+
+void del(int u) {
+    res -= color[c[u]] - 2 * --cnt[c[u]] - 1;
+}
+
+void add(int u, int f) {
+    add(u);
+    for (int v : g[u])
+        if (v != f) add(v, u);
+}
+
+void del(int u, int f) {
+    del(u);
+    for (int v : g[u])
+        if (v != f) del(v, u);
+}
+
+void dfs(int u, int f) {
+    fa[u] = f;
+    siz[u] = 1;
+
+    for (int v : g[u]) {
+        if (v == f) continue;
+
+        dfs(v, u);
+        siz[u] += siz[v];
+        if (siz[v] > siz[son[u]]) son[u] = v;
+    }
+}
+
+void dsu(int u, int f) {
+    for (auto v : g[u]) {
+        if (v == f || v == son[u]) continue;
+
+        dsu(v, u);
+        del(v, u);
+    }
+    if (son[u]) dsu(son[u], u);
+
+    for (auto v : g[u]) {
+        if (v == f || v == son[u]) continue;
+
+        add(v, u);
+    }
+
+    add(u);
+    ans[u] = res;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> c[i];
+
+        color[c[i]]++;
+    }
+
+    for (int i = 1, u, v; i < n; i++) {
+        cin >> u >> v;
+
+        g[u].emplace_back(v);
+        g[v].emplace_back(u);
+        edges.emplace_back(u, v);
+    }
+
+    dfs(1, 1);
+    dsu(1, 1);
+
+    for (auto e : edges) {
+        int u = e.first,
+            v = e.second;
+
+        cout << (fa[u] == v ? ans[u] : ans[v]) << ' ';
+    }
+
+    cout << endl;
+
+    return 0;
+}