Submission #1127200

#	Time	Username	Problem	Language	Result	Execution time	Memory
1127200		czauderna	Duathlon (APIO18_duathlon)	C++20	100 / 100	120 ms	30292 KiB

count_triplets

// Solve dla całego zadnia
// O(n)
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
typedef long long ll;
const int N = 2e5+3;
vector<int> grf[N], tree[N], stos;
ll siz[N], out, ile;
int n, pre[N], low[N], tmr, cnt=1;
void dfs(int v, int p){
	pre[v]=low[v]= ++tmr;
	ile++;
	stos.pb(v);
	for(auto w:grf[v]){
		if(w==p) continue;
		if(!pre[w]){
			dfs(w, v);
			low[v]=min(low[v], low[w]);
			if(low[w]>= pre[v]){
				tree[v].pb(n+cnt);
				while(tree[n+cnt].size()==0 || tree[n+cnt].back()!=w){
					tree[n+cnt].pb(stos.back());
					stos.pop_back();
				}
				cnt++;
			}
		}else low[v]=min(low[v], pre[w]);
	}
}
void dfs2(int v, int p){
	if(v<=n) siz[v]=1;
	for(auto w:tree[v]){
		dfs2(w, v);
		siz[v]+=siz[w];
		if(v>n) out-=(ll)tree[v].size()*siz[w]*(siz[w]-1);
	}
	if(v>n) out-=(ll)tree[v].size()*(ile-siz[v])*(ile-siz[v]-1);
}
int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	int m;
	cin >> n >> m;
	for(int i=0; i<m; i++){
		int a, b;
		cin >> a >> b;
		grf[a].pb(b);
		grf[b].pb(a);
	}
	for(int i=1; i<=n; i++){
		if(pre[i]) continue;
		ile=0;
		dfs(i, i);
		out+=ile*(ile-1)*(ile-2);
		dfs2(i, i);
	}
	cout << out << '\n';
	return 0;
}

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