Submission #1331072

#TimeUsernameProblemLanguageResultExecution timeMemory
1331072i_am_blindfoldDuathlon (APIO18_duathlon)C++20
31 / 100
52 ms18332 KiB
#include <bits/stdc++.h>
using namespace std;

const int N = 1e5 + 5;

vector<pair<int, int>> adj[N];
vector<int> vis(N, 0), siz(N, 1), tin(N), low(N);
long long ans = 0;

void dfs_size(int u, int ip, int& sz) {
    vis[u] = 1, sz++;
    for (auto &[v, i]: adj[u]) {
        if (i == ip) continue;
        if (vis[v]) continue;
        dfs_size(v, i, sz); 
    }
}

void dfs(int u, int ip, int& t, int n) {
    low[u] = tin[u] = t++, vis[u] = 2;
    int sz = n - 1;
    for (auto &[v, i]: adj[u]) {
        if (i == ip) continue;
        if (vis[v] == 1) {
            dfs(v, i, t, n);
            siz[u] += siz[v];
            low[u] = min(low[u], low[v]);
            if (low[v] >= tin[u]) {
                sz -= siz[v];
                ans += 2LL * (1LL * sz * siz[v] + 1LL * n * (t - tin[u] - 1) * (t - tin[u] - 2)) - 1LL * (t - tin[u]) * (t - tin[u] - 1) * (t - tin[u] - 2);
                t = tin[u] + 1;
            } 
        } else {
            low[u] = min(low[u], tin[v]); 
        }
    }
}

int main() {
    ios::sync_with_stdio(false); 
    cin.tie(nullptr);

    int n, m;
    cin >> n >> m;

    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back({v, i});
        adj[v].push_back({u, i});
    }

    for (int i = 1, t = 0; i <= n; i++) {
        if (!vis[i]) {
            int sz = 0;
            dfs_size(i, - 1, sz);
            dfs(i, - 1, t, sz);
        }
    }

    cout << ans << '\n';
    
    return 0;
}
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