Submission #1115776

#	Time	Username	Problem	Language	Result	Execution time	Memory
1115776		gustavo_d	Duathlon (APIO18_duathlon)	C++17	8 / 100	45 ms	14236 KiB

count_triplets

// https://oj.uz/problem/view/APIO18_duathlon > p520
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
const int MAXN = 1e5;
vector<int> adj[MAXN];
bool vis[MAXN];

pair<int, bool> dfs(int v, int pai) {
	vis[v] = true;
	int sz = 1;
	bool cycle = false;
	for (int viz : adj[v]) {
		if (vis[viz]) {
			if (viz != pai) cycle = true;
			continue;
		}
		pair<int, int> res = dfs(viz, v);
		sz += res.first;
		if (res.second) cycle = true;
	}
	return {sz, cycle};
}

ll qty(pair<int, bool> res) {
	int n = res.first; bool cycle = res.second;
	return (ll)(n) * (ll)(n - 1) * (ll)(n - 2) / (ll)(3 - 2*cycle);
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(NULL);

	int n, m; cin >> n >> m;
	for (int i=0; i<m; i++) {
		int u, v; cin >> u >> v;
		u--; v--;
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	ll ans = 0;
	for (int i=0; i<n; i++) {
		if (vis[i]) continue;
		// assert(i==0);
		ans += qty(dfs(i, -1));
	}
	cout << ans << '\n';

	return 0;
}

• 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