제출 #1335272

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1335272		aaaaaaaa	철인 이종 경기 (APIO18_duathlon)	C++20	0 / 100	1111 ms	1114112 KiB

count_triplets

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

const int mxN = 2e5 + 100;

long long ans = 0;
vector<int> adj[mxN];
int n, m, s[mxN];

void dfs(int u = 1, int par = 0){
    s[u] = 1;
    int total = 0;
    for(auto it : adj[u]){
        if(it ^ par){
            dfs(it, u);
            ans += (long long) total * s[it];
            total += s[it];
        }
    }
    int left = n - total - 1;
    ans += (long long) left * total;
    s[u] += total;
}

signed main(){
	ios_base::sync_with_stdio(0);
	cin.tie(nullptr); cout.tie(nullptr);

	int m;
    cin >> n >> m;

    for(int i = 1, u, v ; i <= m; ++i){
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    dfs();

    cout << (long long) ans * 2 << "\n";

	return 0;
}

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