Submission #1207642

#	Time	Username	Problem	Language	Result	Execution time	Memory
1207642		madamadam3	Duathlon (APIO18_duathlon)	C++20	0 / 100	1108 ms	1114112 KiB

count_triplets

#include <bits/stdc++.h>

using namespace std;

#define int long long int

const int MAXN = 100'001, MAXM = 200'001;
int n, m;

vector<int> adj[MAXN];
int sz[MAXN], tin[MAXN], low[MAXN], par[MAXN];
bool vis[MAXN];

int ways = 0;

void dfs(int u, int p) {
    sz[u] = 1;
    par[u] = p;

    for (int v : adj[u]) {
        if (v == p) continue;
        dfs(v, u);
        sz[u] += sz[v];
    }
}

void dfs2(int u, int p) {
    int contrib = 0;

    for (int v : adj[u]) {
        if (v == p) {
            // contrib += sz[u] * (n - sz[v]);
            ways -= (n - sz[u]) * (n - sz[u] - 1);
            continue;
        }
        dfs2(v, u);
        
        // contrib += sz[v] * (n - sz[v] - 1);
        ways -= sz[v] * (sz[v] - 1);
    }

    // ways += contrib;
    // cout << u << " contributes " << contrib << "\n";
}

signed main() {
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        int u, v; cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    if (n <= 2) {
        cout << 0;
        return 0;
    }

    ways = n * (n - 1) * (n - 2);

    dfs(1, 1);
    dfs2(1, 1);
    
    cout << ways;
    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