제출 #260872

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
260872		emanIaicepsa	철인 이종 경기 (APIO18_duathlon)	C++14	0 / 100	1106 ms	1048580 KiB

count_triplets

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<ll,ll>
#define vi vector<int>
#define pb emplace_back
#define fi first
#define se second
#define all(n) (n).begin(),(n).end()
#define mem(n,m) memset(n,m,sizeof(n))
#define IOS ios::sync_with_stdio(0), cin.tie(0)
#define dbg(...) cerr<<#__VA_ARGS__<<" = ";_do(__VA_ARGS__);
template<typename A> void _do(A x){cerr<<x<<'\n';}
template<typename A,typename ...B> void _do(A x,B ...y){cerr<<x<<", ";_do(y...);}

ll n,m;
vi E[100005];
ll siz[100005], ans=0;

void dfs(int x,int p){
    siz[x] = 1;
    for(auto i:E[x]){
        if(i==p) continue;
        dfs(i,x);
        siz[x] += siz[i];
    }
}

void dfs2(int x,int p){
    for(auto i:E[x]){
        if(i==p) continue;
        dfs2(i,x);
        ans += siz[i] * (n-siz[i]-1);
    }
    ans += (siz[x]-1) * (n-siz[x]);
}

signed main(){
	IOS;
    cin>>n>>m;
    for(int i=1,a,b;i<=m;i++){
        cin>>a>>b;
        E[a].pb(b);
        E[b].pb(a);
    }

    dfs(1,0);
    dfs2(1,0);

    cout<<ans<<'\n';

}

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