Submission #1111183

#	Time	Username	Problem	Language	Result	Execution time	Memory
1111183		vjudge2	Duathlon (APIO18_duathlon)	C++17	0 / 100	104 ms	30140 KiB

count_triplets

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

#define int long long

const int N = 1e5 + 10;
vector<int> adj[N], g[N << 1], stk;
int n, m, st[N], low[N], timer = 0, k, we[N << 1], sz[N << 1], ans = 0, p[N];
bool vis[N << 1];

int find(int u) {
    return p[u] == u ? u : p[u] = find(p[u]);
}

void merge(int u, int v) {
    u = find(u), v = find(v);
    p[v] = u;
}

void dfs(int u) {
    low[u] = st[u] = ++timer;
    stk.push_back(u);
    for (auto& v : adj[u]) {
        if (!st[v]) {
            dfs(v);
            low[u] = min(low[u], low[v]);
            if (low[v] == st[u]) {
                ++k;
                for (int x = -1; x != v; stk.pop_back()) {
                    x = stk.back();
                    g[k].push_back(x);
                    g[x].push_back(k);
                    merge(x, k);
                    we[k]++;
                }
                g[k].push_back(u);
                g[u].push_back(k);
                merge(u, k);
                we[k]++;
            }
        }
        low[u] = min(low[u], st[v]);
    }
}

void comp(int u, int p) {
    sz[u] = (u <= n);
    vis[u] = true;
    int ch = 0;
    for (int v : g[u]) {
        if (v == p) continue;
        ++ch;
        comp(v, u);
        sz[u] += sz[v];
        // cout << "hi " << u << " " << sz[u] << '\n';
    }
    if (!ch) ans--;
}

void Dfs(int u, int p) {
    int sum = 0;
    vis[u] = true;
    for (int v : g[u]) {
        if (v == p) continue;
        Dfs(v, u);
        sum += sz[v];
    }
    for (int v : g[u]) if (v != p) ans += we[u] * sz[v] * (sum - sz[v]);
    ans += we[u] * sum * (sz[find(u)] - sum);
}

int32_t main() {
    ios::sync_with_stdio(0); cin.tie(0);
    cin >> n >> m;
    if (n <= 2) {
        cout << "0\n";
        return 0;
    }
    k = n;
    for (int i = 1; i <= n; i++) we[i] = -1;
    for (int i = 1; i <= 2 * n; i++) p[i] = i;
    for (int i = 1; i <= m; i++) {
        int u, v;
        cin >> u >> v;
        merge(u, v);
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    for (int i = 1; i <= n; i++) if (!st[i]) dfs(i);
    for (int i = 1; i <= k; i++) if (!vis[i]) comp(i, -1);
    for (int i = 1; i <= k; i++) vis[i] = false;
    for (int i = 1; i <= k; i++) if (!vis[i]) ans--, Dfs(i, -1);
    // for (int i = 1; i <= n; i++) cout << sz[find(i)] << '\n';
    cout << ans << '\n';
}

• 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