Submission #1160942

#	Time	Username	Problem	Language	Result	Execution time	Memory
1160942		not_amir	Duathlon (APIO18_duathlon)	C++20	0 / 100	53 ms	25412 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

vector<int> depth, w;
vector<bool> visited, is_root;
vector<vector<int>> child, nchild;

int dfsc(int v, int r) {
    int cnt = 1;
    for (int u : child[v]) {
        if (is_root[u])
            nchild[r].push_back(u);
        else
            cnt += dfsc(u, r);
    }
    return cnt;
}

int dfs1(int v, int p, vector<vector<int>> &G, int d = 0) {
    visited[v] = true;
    depth[v] = d;
    int low = d;
    for (int u : G[v]) {
        if (visited[u]) {
            if (u != p)
            low = min(low, depth[u]);
            continue;
        }
        child[v].push_back(u);
        int curr = dfs1(u, v, G, d + 1);
        if (curr > d) {
            w[u] = dfsc(u, u);
            is_root[u] = true;
        }
        low = min(low, curr);
    }
    return low;
}

ll ans = 0;

int dfs2(int v, int n) {
    vector<int> S;
    int siz = w[v];
    for (int u : nchild[v]) {
        S.push_back(dfs2(u, n));
        siz += S.back();
    }
    int curr = n - siz;
    for (int s : S) {
        ans += curr * s * w[v];
        curr += s;
    }
    return siz;
}

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int n, m;
    cin >> n >> m;
    vector<vector<int>> G(n + 1);
    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        G[u].push_back(v);
        G[v].push_back(u);
    }
    visited.resize(n + 1);
    depth.resize(n + 1);
    child.resize(n + 1);
    nchild.resize(n + 1);
    w.resize(n + 1);
    is_root.resize(n + 1);
    dfs1(1, 0, G);
    w[1] = dfsc(1, 1);
    dfs2(1, n);
    ans *= 2;
    ll sum1 = 0, sum2 = 0;
    for (int i = 1; i <= n; i++) {
        ans += sum1 * w[i] * (w[i] - 1);
        ans += sum2 * w[i];
        sum1 += w[i];
        sum2 += w[i] * (w[i] - 1);
        ans += w[i] * (w[i] - 1) * (w[i] - 2);
    }
    cout << ans << '\n';
}

/*
7 6
1 2
2 3
2 4
2 5
5 6
5 7
 */

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 8
• Subtask 4: 0 / 10
• Subtask 5: 0 / 13
• Subtask 6: 0 / 15
• Subtask 7: 0 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10