Submission #710245

#	Time	Username	Problem	Language	Result	Execution time	Memory
710245		vjudge1	Duathlon (APIO18_duathlon)	C++17	23 / 100	87 ms	15632 KiB

count_triplets

/*
Author : DeMen100ns (a.k.a Vo Khac Trieu)
School : VNU-HCM High school for the Gifted
fuck you adhoc
*/

#include <bits/stdc++.h>
#define endl '\n'

#define int long long

using namespace std;

const int N = 3e5 + 5;
const long long INF = 1e18 + 7;
const int MAXA = 1e9;
const int B = sqrt(N) + 5;

vector <int> a[N];
int sub[N]; bool f[N], g[N];
int ans = 0, n;

void dfs(int root, int u, int par = 0){
    f[u] = true;
    int sum = 0;
    for(int i : a[u]){
        if (i == par) continue;
        dfs(root, i, u);

        ans += sum * sub[i];
        sum += sub[i];
    }
    ans += (sub[root] - sub[u]) * (sub[u] - 1);
}

void dfs_precal(int u, int par = 0){
    sub[u] = 1;
    for(int i : a[u]){
        if (i == par) continue;
        dfs_precal(i, u);

        sub[u] += sub[i];
    }
}

bool F;
int ct;

void dfs_check(int u, int par, bool g[]){
    ++ct;
    g[u] = true;
    for(int i : a[u]){
        if (i == par) continue;
        if (g[i]){
            F = false;
            continue;
        }

        dfs_check(i, u, g);
    }
}

void solve()
{
    int m; cin >> n >> m;
    for(int i = 1; i <= m; ++i){
        int u, v; cin >> u >> v;
        a[u].push_back(v);
        a[v].push_back(u);
    }

    for(int i = 1; i <= n; ++i){
        if (!f[i]){
            F = true; ct = 0;
            dfs_check(i, 0, g);

            if (F){
                dfs_precal(i);
                dfs(i, i);
            } else {
                ans += ct * (ct - 1) * (ct - 2);
                dfs_check(i, 0, f);
            }
        }
    }

    cout << 2ll * ans;
}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    // freopen("codeforces.inp","r",stdin);
    // freopen("codeforces.out","w",stdout);

    int t = 1; // cin >> t;
    while (t--)
    {
        solve();
    }
}

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