제출 #771789

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
771789		gagik_2007	철인 이종 경기 (APIO18_duathlon)	C++17	0 / 100	102 ms	16348 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];
ll sz[N];

void dfs(int v, int par=-1){
    sz[v]=1;
    for(int to:g[v]){
        if(to!=par){
            dfs(to,v);
            sz[v]+=sz[to];
        }
    }
}

void calc_ans(int c, int v, ll& ans, int par=-1){
    ll sum=0;
    for(int to:g[v]){
        if(to!=par){
            calc_ans(c,to,ans,v);
            ans+=sz[to]*(c-sz[to]-1);
            sum+=sz[to];
        }
    }
    ans+=sum*(c-sum-1);
}

int main() {
    cin>>n>>m;
    assert(m==n-1);
    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=1;v<=n;v++){
        if(sz[v]==0){
            dfs(v);
            calc_ans(sz[v],v,ans);
        }
    }
    cout<<ans<<endl;
}

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