Submission #983148

#	Time	Username	Problem	Language	Result	Execution time	Memory
983148		vjudge1	Duathlon (APIO18_duathlon)	C++17	31 / 100	47 ms	19592 KiB

count_triplets

#include <bits/stdc++.h>
#define int long long
using namespace std;
int n, m, i, j, x, y, ans, sz[200001], rt[200001];
bool u[200001], cyc, cyc2[200001];
vector<int> g[200001];
vector<pair<int, int>> v;

void dfs(int x, int pr, int r) {
	sz[x] = 1;
	u[x] = 1;
	rt[x] = r;
	for (auto y : g[x]) {
		if (y == pr) continue;
		if (u[y]) {
			cyc = 1;
			continue;
		}
		dfs(y, x, r);
		sz[x] += sz[y];
	}
}

signed main() {
	cin.tie(0)->sync_with_stdio(0);
	#ifdef LOCAL
	freopen("input.txt", "r", stdin);
	#endif
	cin >> n >> m;
	while (m--) {
		cin >> x >> y;
		g[x].push_back(y);
		g[y].push_back(x);
	}
	for (i = 1; i <= n; i++) {
		if (!u[i]) {
			cyc = 0;
			dfs(i, i, i);
			v.push_back({i, cyc});
		}
	}
	for (auto i : v) {
		if (!i.second) ans -= (sz[i.first]) * (sz[i.first] - 1);
		else {
			cyc2[i.first] = 1;
			ans += (sz[i.first]) * (sz[i.first] - 1) * (sz[i.first] - 2);
		}
	}
	for (i = 1; i <= n; i++) {
		if (!cyc2[rt[i]]) {
			ans += 2 * (sz[i] - 1) * (sz[rt[i]] - sz[i]);
			ans += 2 * (sz[rt[i]] - sz[i]);
		}
	}
	cout << ans;
}

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