Submission #980790

#	Time	Username	Problem	Language	Result	Execution time	Memory
980790		Unforgettablepl	Duathlon (APIO18_duathlon)	C++17	8 / 100	41 ms	19292 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;

#define int long long

vector<int> adj[200001];
bool visited[200001];
int DP[200001][4];
bool isCycle;
int tot;

void dfs(int x,int p){
    if(visited[x]){
        isCycle=true;
        return;
    }
    tot++;
    visited[x]=true;
    for(int&i:adj[x])if(i!=p)dfs(i,x);
}

int32_t main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    for(auto&i:DP)i[0]=1;
    for(int i=1;i<=200000;i++)for(int j=1;j<=3;j++)DP[i][j]=DP[i-1][j]+DP[i-1][j-1];
    int n,m;
    cin >> n >> m;
    for(int i=1;i<=m;i++){
        int a,b;cin>>a>>b;
        adj[a].emplace_back(b);
        adj[b].emplace_back(a);
    }
    int ans = 0;
    for(int i=1;i<=n;i++)if(!visited[i]){
        isCycle = false;
        tot = 0;
        dfs(i,0);
        if(isCycle)ans+=tot*(tot-1ll)*(tot-2ll);
        else ans+=2ll*DP[tot][3];
    }
    cout << ans << '\n';
}

• 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