Submission #408099

#	Time	Username	Problem	Language	Result	Execution time	Memory
408099		tengiz05	철인 이종 경기 (APIO18_duathlon)	C++17	0 / 100	84 ms	10476 KiB

count_triplets

#include <bits/stdc++.h>
using i64 = long long;
constexpr int N = 1e5;
std::vector<int> e[N];
int n, m;
std::vector<bool> vis;
bool cycle;
int sz;
void dfs(int u, int p) {
    sz++;
    vis[u] = true;
    for (auto v : e[u]) {
        if (v == p)continue;
        if (vis[v]) cycle = true;
        else dfs(v, u);
    }
}
i64 ans;
int calc(int u, int p) {
    int cnt = 0;
    for (auto v : e[u]) {
        if (v != p) {
            cnt += calc(v, u);
        }
    }
    ans += i64(cnt) * (sz - cnt - 1) * 2ll;
    return cnt + 1;
}
int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::cin >> n >> m;
    for (int i = 0; i < m; i++) {
        int u, v;
        std::cin >> u >> v;
        u--;
        v--;
        e[u].push_back(v);
        e[v].push_back(u);
    }
    vis.assign(n, false);
    for (int i = 0; i < n; i++) {
        if (!vis[i]) {
            sz = 0;
            cycle = false;
            dfs(i, i);
            if (cycle) {
                ans += i64(sz) * i64(sz - 1) * i64(sz - 2) / 3ll * 2ll;
            } else {
                calc(i, i);
            }
        }
    }
    std::cout << ans << '\n';
    return 0;
}

• 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