제출 #370662

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
370662		Leonardo_Paes	철인 이종 경기 (APIO18_duathlon)	C++17	0 / 100	1114 ms	1048580 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ar array
#define sz(a) ((int)(a).size())
#define all(a) (a).begin(),(a).end()
typedef pair<int,int> pii;
#define f first
#define s second
const int maxn = 1e5+10;
vector<int> grafo[maxn];
int n, m, dp[maxn], sz[maxn], qtd2[maxn];
int solve(int u, int p = 0){ // lca of path is u, 1 as a root
    int ans = 0; // sum of dps
    sz[u] = 1;
    for(int v : grafo[u]){
        if(v == p) continue;
        ans += solve(v, u);
        sz[u] += sz[v];
        qtd2[u] += qtd2[v] + sz[v];
    }
    int qtd = sz[u] - 1;
    for(int v : grafo[u]){
        if(v == p) continue;
        qtd -= sz[v];
        dp[u] += sz[v] * qtd;
        dp[u] += (sz[u]  - sz[v]) * qtd2[v];
    }
    return ans + dp[u];
}
int32_t main(){
    ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
    cin >> n >> m;
    for(int i=1; i<=m; i++){
        int u, v;
        cin >> u >> v;
        grafo[u].push_back(v);
        grafo[v].push_back(u);
    }
    cout << 2*solve(1) << "\n";
    return 0;
}

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