Submission #374632

#	Time	Username	Problem	Language	Result	Execution time	Memory
374632		morato	철인 이종 경기 (APIO18_duathlon)	C++17	0 / 100	1150 ms	1048576 KiB

count_triplets

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

const int N = 1e5 + 5;

long long ans;
vector<int> adj[N];
int subtree[N], n;

void dfs(int v, int p = 0) {
    subtree[v] = 1;
    for (int u : adj[v]) if (u != p) {
        dfs(u, v);
        subtree[v] += subtree[u];
    }
    vector<long long> pref;
    pref.push_back(n - subtree[v]);
    long long local_ans = 0;
    for (int u : adj[v]) if (u != p) {
        assert(!pref.empty());
        local_ans += pref.back() * 1ll * subtree[u];
        pref.push_back(pref.back() + 1ll * subtree[u]);
    }
    ans += 2ll * local_ans;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int m; cin >> n >> m;
    for (int i = 0; i < m; i++) {
        int a, b; cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    for (int i = 1; i <= n; i++) {
    	if (!subtree[i]) {
    		dfs(i);
    	}
    }
    cout << ans << '\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