59 lines
1.3 KiB
C++
59 lines
1.3 KiB
C++
#include <iostream>
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#include <vector>
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#include <queue>
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using namespace std;
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const int maxn = 300010;
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int main() {
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ios::sync_with_stdio(false);
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cin.tie(0);
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int n;
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cin >> n;
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vector<vector<int>> g(n + 1);
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for (int i = 0; i < n - 1; i++) {
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int u, v;
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cin >> u >> v;
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g[u].push_back(v);
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g[v].push_back(u);
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}
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vector<int> fa(n + 1, 0);
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vector<int> dep(n + 1, 0);
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vector<long long> size_arr(n + 1, 1);
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vector<long long> sum_sq(n + 1, 0);
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vector<int> nodes;
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queue<int> q;
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q.push(1);
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fa[1] = 0;
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dep[1] = 0;
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while (!q.empty()) {
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int u = q.front();
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q.pop();
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nodes.push_back(u);
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for (int v : g[u]) {
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if (v == fa[u]) continue;
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fa[v] = u;
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dep[v] = dep[u] + 1;
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q.push(v);
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}
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}
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for (int i = nodes.size() - 1; i >= 0; i--) {
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int u = nodes[i];
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if (fa[u] != 0) {
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size_arr[fa[u]] += size_arr[u];
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sum_sq[fa[u]] += size_arr[u] * size_arr[u];
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}
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}
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long long ans = 0;
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for (int u = 1; u <= n; u++) {
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long long count_u = size_arr[u] * size_arr[u] - sum_sq[u];
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ans += (long long)u * count_u;
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}
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cout << ans << endl;
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return 0;
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} |