Submission #546790

#	Time	Username	Problem	Language	Result	Execution time	Memory
546790		Monarchuwu	Duathlon (APIO18_duathlon)	C++17	8 / 100	26 ms	2384 KiB

count_triplets

#include<iostream>
#include<algorithm>
using namespace std;
typedef long long ll;

const int N = 1e5 + 9;
int n, m, deg[N];

int par[N];
int root(int u) { return par[u] < 0 ? u : par[u] = root(par[u]); }
void Union(int u, int v) {
    if ((u = root(u)) == (v = root(v))) return;
    if (par[u] > par[v]) swap(u, v);
    par[u] += par[v];
    par[v] = u;
}

ll calc2(int n) {
    return (ll)n * (n - 1) * (n - 2);
}
ll calc(int n) {
    return calc2(n) / 3;
}

bool f[N];
int main() {
    cin.tie(NULL)->sync_with_stdio(false);
    cin >> n >> m;
    fill(par + 1, par + n + 1, -1);
    for (int i = 0, u, v; i < m; ++i) {
        cin >> u >> v;
        Union(u, v);
        ++deg[u], ++deg[v];
    }

    for (int i = 1; i <= n; ++i)
        if (deg[i] == 1) f[root(i)] = true;

    ll ans(0);
    for (int i = 1; i <= n; ++i)
        if (par[i] < 0) ans += f[i] ? calc(-par[i]) : calc2(-par[i]);
    cout << ans << '\n';
}
/**  /\_/\
 *  (= ._.)
 *  / >0  \>1
**/

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 8 / 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