Submission #218592

#	Time	Username	Problem	Language	Result	Execution time	Memory
218592		VEGAnn	Duathlon (APIO18_duathlon)	C++14	100 / 100	240 ms	33008 KiB

count_triplets

#include <bits/stdc++.h>
#define PB push_back
using namespace std;
typedef long long ll;
const int N = 100100;
const int M = 200100;
set<int> st;
vector<int> g[N], adj[2 * M];
int n, m, tin[N], fup[N], pr[M], siz_comp[2 * M], siz[2 * M], tt = 0, U[M], V[M];
bool mrk[2 * M];
ll ans = 0ll;

int get(int x){ return (pr[x] == x ? x : pr[x] = get(pr[x])); }

void dfs0(int v, int p_edg){
    mrk[v] = 1;
    tin[v] = fup[v] = ++tt;

    for (int nm : g[v]){
        if (nm == p_edg) continue;

        int u = (U[nm] == v ? V[nm] : U[nm]);

        if (!mrk[u]){
            dfs0(u, nm);

            if (fup[u] < tin[v]){
                if (p_edg >= 0) pr[get(p_edg)] = get(nm);
            }

            fup[v] = min(fup[v], fup[u]);
        } else {
            fup[v] = min(fup[v], tin[u]);

            if (tin[u] < tin[v])
                pr[get(p_edg)] = get(nm);
        }
    }
}

void dfs(int v, int p){
    mrk[v] = 1;
    siz[v] = bool(v < n);

    for (int u : adj[v])
        if (u != p) {
            dfs(u, v);
            siz[v] += siz[u];
        }
}

void finally(int v, int r, int p){
    if (v < n){
        for (int u : adj[v])
            if (u == p)
                ans -= (ll(siz_comp[u - n]) - 1ll) * ll(siz[v]) * (ll(siz[v]) - 1ll);
            else ans -= (ll(siz_comp[u - n]) - 1ll) * (ll(siz[r]) - ll(siz[u])) * (ll(siz[r]) - ll(siz[u]) - 1ll);
    }

    for (int u : adj[v]){
        if (u == p) continue;
        finally(u, r, v);
    }
}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);

//    freopen("in.txt","r",stdin);

    cin >> n >> m;

    for (int i = 0; i < m; i++){
        pr[i] = i;

        int x, y; cin >> x >> y;
        x--; y--;

        U[i] = x;
        V[i] = y;
        g[x].PB(i);
        g[y].PB(i);
    }

    for (int i = 0; i < n; i++)
        if (!mrk[i]) dfs0(i, -1);

    for (int v = 0; v < n; v++){
        st.clear();

        for (int nm : g[v])
            st.insert(get(nm));

        for (auto cp : st){
            siz_comp[cp]++;
            adj[cp + n].PB(v);
            adj[v].PB(cp + n);
        }
    }

    fill(mrk, mrk + n, 0);

    for (int v = 0; v < n; v++){
        if (mrk[v]) continue;

        dfs(v, -1);
        ans += ll(siz[v]) * (ll(siz[v]) - 1ll) * (ll(siz[v]) - 2ll);
        finally(v, v, -1);
    }

    cout << ans;

    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