Submission #217691

#	Time	Username	Problem	Language	Result	Execution time	Memory
217691		VEGAnn	Duathlon (APIO18_duathlon)	C++14	66 / 100	201 ms	20600 KiB

count_triplets

#include <bits/stdc++.h>
#define all(x) x.begin(),x.end()
#define sz(x) ((int)x.size())
#define PB push_back
#define pii pair<int,int>
#define ft first
#define sd second
#define MP make_pair
using namespace std;
typedef long long ll;
const int N = 100100;
const int M = 200100;
const int oo = 2e9;
vector<int> g[N];
vector<pii> 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], cutpoint[N], cp[N], used[N];
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 (pii u : gr[v]){
        if (u.sd == p) continue;

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

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

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

    ll sum = 0ll;

    for (int it = 0; it < sz(gr[v]); ){

        int j = it;
        ll sim = 0;

        while (j < sz(gr[v]) && gr[v][it].ft == gr[v][j].ft){
            int u = gr[v][j].sd;
            if (u != p) {
                dfs2(u, v);
                ans += sim * ll(nw_siz[u]);
                sim += ll(nw_siz[u]);
            } else {
                ans += sim * (SZ - ll(nw_siz[v]));
                sim += (SZ - ll(nw_siz[v]));
            }
            j++;
        }

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

        sum += sim;

        it = j;
    }
}

void search_cutpoint(int v, int p){
    mrk[v] = 1;
    tin[v] = fup[v] = ++tt;
    int children = 0;

    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 {
            children++;
            search_cutpoint(u, v);
            fup[v] = min(fup[v], fup[u]);

            if (fup[u] >= tin[v] && p >= 0){
                cutpoint[v] = 1;
            }
        }
    }

    if (p < 0 && children > 1)
        cutpoint[v] = 1;
}

void last_dfs(int v){
    if (cp[v] || used[v]) return;
    used[v] = 1;
    ans++;

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

void dfser(int v, int p, int st){
    if (mrk[v]) return;
    mrk[v] = 1;

    if (cutpoint[v])
        cp[v] = 1;

    if (v != st){
        fill(used, used + n, 0);
        used[v] = 1;

        for (int nm : g[v]){
            int u = (U[nm] == v ? V[nm] : U[nm]);
            if (u == p) continue;
            last_dfs(u);
        }
    }

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

        dfser(u, v, st);
    }

    if (cutpoint[v])
        cp[v] = 0;
}

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);
    }

    if (n <= 50 && m <= 100){

        for (int i = 0; i < n; i++){
            if (mrk[i]) continue;
            search_cutpoint(i, -1);
        }

        for (int st = 0; st < n; st++){
            fill(mrk, mrk + n, 0);
            dfser(st, -1, st);
        }

        cout << ans;

        return 0;
    }

    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(MP(U[i], y));
            gr[y].PB(MP(V[i], x));
        }

    fill(mrk, mrk + n, 0);
    for (int i = 0; i < n; i++)
        if (sz(gr[i])){
            sort(all(gr[i]));
        }

    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: 8 / 8
• Subtask 4: 10 / 10
• Subtask 5: 13 / 13
• Subtask 6: 15 / 15
• Subtask 7: 20 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10