Submission #356496

#	Time	Username	Problem	Language	Result	Execution time	Memory
356496		valerikk	Duathlon (APIO18_duathlon)	C++11	100 / 100	291 ms	33772 KiB

count_triplets

#include <bits/stdc++.h>

using namespace std;

const int N = 2e5 + 7;

int n, m;
vector<int> g[N], g_[N];
int dep[N], low[N];
bool vis[N];
int cnt;
int sub[N];
long long ans = 0;

void prepare_dfs(int u, int par = -1) {
    vis[u] = true;
    low[u] = dep[u];
    for (int v : g[u]) {
        if (v == par)
            continue;
        if (!vis[v]) {
            dep[v] = dep[u] + 1;
            prepare_dfs(v, u);
            low[u] = min(low[u], low[v]);
        } else {
            low[u] = min(low[u], dep[v]);
        }
    }
}

void add_edge(int u, int v, int c) {
    g_[u].push_back(c);
    g_[c].push_back(u);
    g_[v].push_back(c);
    g_[c].push_back(v);
}

void dfs(int u, int c = -1, int par = -1) {
    vis[u] = true;
    for (int v : g[u]) {
        if (v == par)
            continue;
        if (!vis[v]) {
            int c_ = c;
            if (dep[u] <= low[v])
                c_ = ++cnt;
            add_edge(u, v, c_);
            dfs(v, c_, u);
        } else {
            if (dep[u] > dep[v])
                add_edge(u, v, c);
        }
    }
}

int get_subtree(int u, int par = -1) {
    vis[u] = true;
    sub[u] = u <= n;
    for (int v : g[u]) {
        if (v != par)
            sub[u] += get_subtree(v, u);
    }
    return sub[u];
}

void count_bad(int u, int total, int par = -1) {
    vis[u] = true;
    for (int v : g[u]) {
        if (v != par)
            count_bad(v, total, u);
    }
    if (u > n) {
        int a = g[u].size();
        for (int v : g[u]) {
            int b = v == par ? total - sub[u] : sub[v];
            ans -= (long long)(a - 1) * b * (b - 1);
        }
    }
}

int main() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
#endif
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
    while (m--) {
        int u, v;
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    for (int i = 1; i <= n; ++i)
        vis[i] = false;
    for (int i = 1; i <= n; ++i) {
        if (!vis[i])
            prepare_dfs(i);
    }
    for (int i = 1; i <= n; ++i)
        vis[i] = false;
    cnt = n;
    for (int i = 1; i <= n; ++i) {
        if (!vis[i])
            dfs(i);
    }
    for (int i = 1; i <= cnt; ++i)
        g[i] = g_[i];
    for (int i = 1; i <= cnt; ++i) {
        sort(g[i].begin(), g[i].end());
        g[i].erase(unique(g[i].begin(), g[i].end()), g[i].end());
    }
    for (int i = 1; i <= cnt; ++i) {
        if (!vis[i]) {
            int total = get_subtree(i);
            ans += (long long)total * (total - 1) * (total - 2);
            count_bad(i, total);
        }
    }
    cout << ans << endl;
    return 0;
}

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