제출 #771794

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
771794		gagik_2007	철인 이종 경기 (APIO18_duathlon)	C++17	8 / 100	105 ms	15360 KiB

count_triplets

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

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

ll ttt;
const ll INF=1e18;
const ll MOD=1e9+7;
const ll N=3e5+7;
ll n,m,k;
vector<int>g[N];
bool used[N];
bool cu[N];

bool is_cycle(int v, int par){
    if(used[v])return true;
    used[v]=true;
    for(int to:g[v]){
        if(to!=par){
            if(is_cycle(to, v))return true;
        }
    }
    return false;
}

int length(int v){
    cu[v]=true;
    int cnt=1;
    for(int to:g[v]){
        if(!cu[to]){
            cnt+=length(to);
        }
    }
    return cnt;
}

int main() {
    cin>>n>>m;
    for(int i=0;i<m;i++){
        int x,y;
        cin>>x>>y;
        g[x].push_back(y);
        g[y].push_back(x);
    }
    ll ans=0;
    for(int v=0;v<n;v++){
        if(!used[v]){
            ll cnt=length(v);
            if(is_cycle(v, v)){
                ans+=cnt*(cnt-1)*(cnt-2);
            }
            else{
                ans+=cnt*(cnt-1)*(cnt-2)/3;
            }
        }
    }
    cout<<ans<<endl;
}

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