Submission #369830

#	Time	Username	Problem	Language	Result	Execution time	Memory
369830		abc864197532	Duathlon (APIO18_duathlon)	C++17	31 / 100	216 ms	45664 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
#define lli long long int
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define test(x) cout << "Line(" << __LINE__ << ") " #x << ' ' << x << endl
#define printv(x) {\
	for (auto i : x) cout << i << ' ';\
	cout << endl;\
}
#define pii pair <int, int>
#define pll pair <lli, lli>
#define X first
#define Y second
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
template<typename A, typename B>
ostream& operator << (ostream& o, pair<A, B> a){
    return o << a.X << ' ' << a.Y;
}
template<typename A, typename B>
istream& operator >> (istream& o, pair<A, B> &a){
    return o >> a.X >> a.Y;
}
const int mod = 1e9 + 7, abc = 864197532, N = 100000, logN = 17, K = 333;

vector <int> adj[N], bcc[N], cnt[N];
int low[N], dep[N], nbcc = 0;
bool vis[N], cut[N];
stack <int> stk;

void dfs(int v, int pa) {
    vis[v] = true;
    low[v] = dep[v] = ~pa ? dep[pa] + 1 : 0;
    stk.push(v);
    int ch = 0;
    for (int u : adj[v]) if (u != pa) {
        if (vis[u]) low[v] = min(low[v], dep[u]);
        else {
            dfs(u, v);
            low[v] = min(low[v], low[u]);
            ch++;
            if (low[u] >= dep[v]) {
                cut[v] = true;
                int x;
                do {
                    x = stk.top(); stk.pop();
                    bcc[x].pb(nbcc);
                    cnt[nbcc].pb(x);
                } while (x != u);
                cnt[nbcc].pb(v);
                bcc[v].pb(nbcc++);
            }
        }
    }
    if (pa == -1 && ch < 2) cut[v] = false;
}

vector <int> newadj[N * 2];
bool vis2[N * 2];
int sz[N * 2], p[N * 2], val[N * 2];
vector <int> cc;

lli C2(int n) {
    return 1ll * n * (n - 1);
}

void dfs2(int v, int pa) {
    sz[v] = val[v];
    vis2[v] = true;
    p[v] = pa;
    cc.pb(v);
    for (int u : newadj[v]) if (u != pa) {
        dfs2(u, v);
        sz[v] += sz[u];
    }
}

int main () {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m;
    cin >> n >> m;
    for (int i = 0, u, v; i < m; ++i) {
        cin >> u >> v, --u, --v;
        adj[u].pb(v);
        adj[v].pb(u);
    }
    for (int i = 0; i < n; ++i) if (!vis[i]) dfs(i, -1);
    for (int i = 0; i < n; ++i) if (cut[i]) {
        for (int j : bcc[i]) {
            newadj[i].pb(j + N);
            newadj[j + N].pb(i);
        }
    }
    for (int i = 0; i < nbcc; ++i) {
        for (int j : cnt[i]) {
            if (!cut[j]) val[i + N]++;
        }
    }
    for (int i = 0; i < n; ++i) if (cut[i]) val[i]++;
    lli ans = 0;
    for (int i = N; i < nbcc + N; ++i) if (!vis2[i]) {
        dfs2(i, -1);
        int m = sz[i];
        if (m <= 2) continue;
        ans += C2(m - 1) * m;
        for (int j : cc) {
            if (j < n) {
                for (int k : newadj[j]) {
                    if (k == p[j]) ans -= C2(m - sz[j] - val[k]);
                    else ans -= C2(sz[k] - val[k]);
                }
            } else {
                for (int k : newadj[j]) {
                    if (k == p[j]) ans -= C2(m - sz[j]) * val[j];
                    else ans -= C2(sz[k]) * val[j];
                }
            }
        }
        cc.clear();
    }
    cout << ans << endl;
}

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