Submission #454885

#	Time	Username	Problem	Language	Result	Execution time	Memory
454885		prvocislo	Duathlon (APIO18_duathlon)	C++17	31 / 100	94 ms	25128 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), col(maxn, -1), my(maxn, 0), stk;
vector<pair<int, int> > e;
int n, m, timer = 0, cnt = 0; 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])
            {
                e.push_back({ u, v });
                while (!stk.empty())
                {
                    int vr = stk.back();
                    col[vr] = cnt, my[cnt]++, stk.pop_back();
                    if (vr == v) break;
                }
                cnt++;
            }
        }
    }
    if (p == -1)
    {
        for (int i : stk) col[i] = cnt, my[cnt]++;
        cnt++; stk.clear();
    }
    return siz;
}
void dfs2(int S, int u, int p = -1)
{
    siz[u] = my[u];
    for (int v : g2[u]) if (v != p)
    {
        dfs2(S, v, u); siz[u] += siz[v];
        ans -= my[u] * 1ll * siz[v] * 1ll * (siz[v] - 1);
    }
    ans -= my[u] * 1ll * (S - siz[u]) * 1ll * (S - siz[u] - 1);
    ans -= (my[u] - 1) * 2ll * (S - my[u]);
}
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);
    for (int i = 0; i < n; i++) if (tin[i] == -1)
    {
        e.clear();
        ll vr = dfs1(i);
        ans += vr * (vr - 1) * (vr - 2);
        for (pair<int, int> j : e) g2[col[j.first]].push_back(col[j.second]), g2[col[j.second]].push_back(col[j.first]);
        dfs2(vr, col[i]);
    }
    cout << ans << "\n";
    return 0;
}

• 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