제출 #844811

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
844811		irmuun	Duathlon (APIO18_duathlon)	C++17	23 / 100	992 ms	1048576 KiB

count_triplets

#include<bits/stdc++.h>
 
using namespace std;
 
#define ll long long
#define pb push_back
#define ff first
#define ss second
#define all(s) s.begin(),s.end()
#define rall(s) s.rbegin(),s.rend()

int main(){
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    ll n,m;
    cin>>n>>m;
    vector<ll>adj[n+1];
    for(ll i=1;i<=m;i++){
        ll u,v;
        cin>>u>>v;
        adj[u].pb(v);
        adj[v].pb(u);
    }
    ll ans=0;
    vector<ll>cnt(n+1,0);
    ll cur=0;
    function <void(ll,ll)> dfs=[&](ll x,ll p){
        cnt[x]=1;
        vector<ll>v;
        for(ll y:adj[x]){
            if(y!=p){
                dfs(y,x);
                v.pb(cnt[y]);
                cnt[x]+=cnt[y];
            }
        }
        v.pb(cur-cnt[x]);
        for(ll y:v){
            ans+=(cur-1-y)*y;
        }
    };
    function<void(ll,ll)> count=[&](ll x,ll p){
        cur++;
        for(auto y:adj[x]){
            if(y!=p){
                count(y,x);
            }
        }
    };
    for(ll i=1;i<=n;i++){
        if(cnt[i]==0){
            cur=0;
            count(i,-1);
            dfs(i,-1);
        }
    }
    cout<<ans;
}

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