Submission #1335275

#	Time	Username	Problem	Language	Result	Execution time	Memory
1335275		aaaaaaaa	철인 이종 경기 (APIO18_duathlon)	C++20	0 / 100	43 ms	9956 KiB

count_triplets

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

const int mxN = 2e5 + 100;

vector<int> adj[mxN];
int n, m, ans = 0, 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 += total * s[it];
            total += s[it];
        }
    }
    int left = n - total - 1;
    ans += left * total;
    s[u] += total;
}

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

    cin >> n >> m;
    assert(n - 1 == 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 << ans * 2ll << "\n";

	return 0;
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 8
• Subtask 4: 0 / 10
• Subtask 5: 0 / 13
• Subtask 6: 0 / 15
• Subtask 7: 0 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10