Submission #260931

#	Time	Username	Problem	Language	Result	Execution time	Memory
260931		wiwiho	Duathlon (APIO18_duathlon)	C++14	31 / 100	180 ms	33656 KiB

count_triplets

#include <bits/stdc++.h>

#define eb emplace_back
#define mp make_pair
#define F first
#define S second
#define pii pair<int, int>
#define pll pair<ll, ll>
#define printv(a, b) {bool pvs = false; \
for(auto i : a){ \
    if(pvs) b << ' '; \
    b << i; pvs = true; \
} \
b << '\n';}

using namespace std;

typedef long long ll;

const ll MAX = 2147483647;

vector<set<int>> g;
vector<ll> sz, cnt;

ll ans = 0;
void dfs(int now, int p){
    sz[now] = cnt[now];
    for(int i : g[now]){
        if(i == p) continue;
        dfs(i, now);
        sz[now] += sz[i];
    }
}

ll r = 0;
void dfs2(int now, int p){
    vector<ll> tmp;
    ll sum = 0;
    for(int i : g[now]){
        if(i == p) continue;
        dfs2(i, now);
        sum += sz[i];
        tmp.eb(sz[i]);
    }
    sum += r - sz[now];
    tmp.eb(r - sz[now]);
    //cerr << now << " " << cnt[now] << "\n";
    //printv(tmp, cerr);
    for(ll i : tmp){
        ans += (sum - i) * i * cnt[now];
        if(cnt[now] >= 3) ans += i * (cnt[now] - 1) * (cnt[now] - 2) * 2;
        if(cnt[now] >= 2) ans += i * (cnt[now] - 1) * 2;
    }
    ans += cnt[now] * (cnt[now] - 1) * (cnt[now] - 2);
}

vector<vector<int>> tg;
vector<int> bccid;
vector<int> ts, low;
int bcc = 1, tts = 0;
stack<int> st;

void dfst(int now, int p){
    low[now] = ts[now] = tts++;
    st.push(now);
    for(int i : tg[now]){
        if(i == p) continue;
        if(ts[i] != -1) low[now] = min(low[now], ts[i]);
        else{
            dfst(i, now);
            low[now] = min(low[now], low[i]);
        }
    }
    if(low[now] > ts[p] || now == p){
        int lst = -1;
        while(lst != now){
            bccid[st.top()] = bcc;
            lst = st.top();
            cnt[bcc]++;
            st.pop();
        }
        bcc++;
    }
}

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

    int n, m;
    cin >> n >> m;

    g.resize(n + 1);
    sz.resize(n + 1);
    tg.resize(n + 1);
    bccid.resize(n + 1);
    ts.resize(n + 1, -1);
    low.resize(n + 1);
    cnt.resize(n + 1);

    for(int i = 0; i < m; i++){
        int u, v;
        cin >> u >> v;
        tg[u].eb(v);
        tg[v].eb(u);
    }

    for(int i = 1; i <= n; i++){
        if(ts[i] == -1) dfst(i, i);
    }
    //printv(bccid, cerr);
    //printv(cnt, cerr);

    for(int i = 1; i <= n; i++){
        for(int j : tg[i]){
            if(bccid[i] != bccid[j]) g[bccid[i]].insert(bccid[j]);
        }
    }

    for(int i = 1; i <= n; i++){
        if(sz[i]) continue;
        dfs(i, i);
        r = sz[i];
        dfs2(i, 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