Submission #217590

#	Time	Username	Problem	Language	Result	Execution time	Memory
217590		VEGAnn	Duathlon (APIO18_duathlon)	C++14	23 / 100	140 ms	19156 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;
const int oo = 2e9;
vector<int> g[N], gr[N];
int n, m, tin[N], fup[N], tt = 0, U[M], V[M], pr[N], siz[N];
int nw_siz[N];
bool mrk[N], bridge[M];
ll ans = 0, SZ;

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

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

        if (u == p) continue;

        if (mrk[u])
            fup[v] = min(fup[v], tin[u]);
        else {
            dfs(u, v);
            fup[v] = min(fup[v], fup[u]);

            if (fup[u] > tin[v])
                bridge[nm] = 1;
        }
    }
}

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

void dfs1(int v, int p){
    nw_siz[v] = siz[v];
    mrk[v] = 1;

    for (int u : gr[v]){
        if (u == p) continue;

        dfs1(u, v);
        nw_siz[v] += nw_siz[u];
    }
}

void dfs2(int v, int p){
    ans += ll(siz[v]) * (ll(siz[v]) - 1ll) * (ll(siz[v]) - 2ll) / 6ll; // first

    ans += (SZ - ll(siz[v])) * (ll(siz[v])) * (ll(siz[v]) - 1ll);

    ll sum = 0ll;

    for (int u : gr[v]){
        if (u == p) continue;

        dfs2(u, v);

        ans += sum * ll(siz[v]) * ll(nw_siz[u]);

        sum += nw_siz[u];
    }

    ans += sum * ll(siz[v]) * (SZ - ll(nw_siz[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++){
        cin >> U[i] >> V[i];
        U[i]--; V[i]--;

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

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

        pr[i] = i;
        siz[i] = 1;
    }


    for (int i = 0; i < m; i++) {
        if (bridge[i]) continue;

        int x = get(U[i]), y = get(V[i]);

        if (x == y) continue;

        pr[x] = y;
        siz[y] += siz[x];
    }

    for (int i = 0; i < m; i++)
        if (bridge[i]){
            int x = get(U[i]), y = get(V[i]);

            gr[x].PB(y);
            gr[y].PB(x);
        }

    fill(mrk, mrk + n, 0);

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

        dfs1(i, -1);
        SZ = nw_siz[i];
        dfs2(i, -1);
    }

    cout << ans * 2;

    return 0;
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 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