Submission #455021

#	Time	Username	Problem	Language	Result	Execution time	Memory
455021		prvocislo	Duathlon (APIO18_duathlon)	C++17	49 / 100	104 ms	39784 KiB

count_triplets

#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
typedef long long ll;
using namespace std;

const int maxn = 1e5 + 5;
vector<int> g[maxn], g2[maxn * 2], siz(maxn, -1), tin(maxn, -1), low(maxn, -1), stk;
int n, m, timer = 0, cnt; ll ans = 0;
int dfs1(int u, int p = -1)
{
    stk.push_back(u); int siz = 1;
    tin[u] = low[u] = timer++;
    for (int v : g[u]) if (v != p)
    {
        if (tin[v] != -1) low[u] = min(low[u], tin[v]);
        else
        {
            siz += dfs1(v, u);
            low[u] = min(low[v], low[u]);
            if (low[v] >= tin[u]) // nova artikulacia
            {
                g2[u].push_back(cnt);
                while (g2[cnt].empty() || g2[cnt].back() != v)
                {
                    g2[cnt].push_back(stk.back());
                    stk.pop_back();
                }
                cnt++;
            }
        }
    }
    return siz;
}
void dfs2(int S, int u, int p = -1)
{
    siz[u] = (u < n);
    for (int v : g2[u]) if (v != p)
    {
        dfs2(S, v, u); siz[u] += siz[v];
        if (u >= n) ans -= (g2[u].size()) * 1ll * siz[v] * 1ll * (siz[v] - 1);
    }
    if (u >= n) ans -= (g2[u].size()) * 1ll * (S - siz[u]) * 1ll * (S - siz[u] - 1);
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m;
    for (int i = 0, u, v; i < m; i++) cin >> u >> v, g[--u].push_back(--v), g[v].push_back(u);
    cnt = n;
    for (int i = 0; i < n; i++) if (tin[i] == -1)
    {
        ll vr = dfs1(i);
        ans += vr * (vr - 1) * (vr - 2);
        dfs2(vr, i);
    }
    //for (int i = 0; i < 2 * n; i++) for (int j : g2[i]) cout << i << " " << j << "\n";
    cout << ans << "\n";
    return 0;
}

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