Submission #1111867

#	Time	Username	Problem	Language	Result	Execution time	Memory
1111867		Pioneer	Duathlon (APIO18_duathlon)	C++17	100 / 100	91 ms	41804 KiB

count_triplets

#include <bits/stdc++.h>

#pragma GCC optimize("Ofast")

#define ll long long
#define int ll
#define all(v) v.begin(),v.end()
#define sz(s) ((int)s.size())
#define pb push_back
#define F first
#define S second
#define pii pair<int,int>
#define ppb pop_back
#define lb lower_bound
#define ub upper_bound

using namespace std;

const ll inf=1e18;
const int MAX=2e5+10;
const int mod=1e9+7;

int binpow(int a,int n){
    if(!n)return 1;
    if(n%2==1)return a*binpow(a,n-1)%mod;
    int k=binpow(a,n/2);
    return k*k%mod;
}

int n,m;
vector<int> g[MAX];
int tin[MAX],timer;
int fup[MAX];
bool use[MAX],cutPoint[MAX];
stack<int> st;
vector<int> ver[MAX];
vector<int> g1[MAX];
int cmp[MAX],cnt;

void dfs(int v,int p=-1){
    st.push(v);
    tin[v]=fup[v]=++timer;
    use[v]=1;
    int children=0;
    for(auto to:g[v]){
        if(to==p)continue;
        if(!use[to]){
            children++;
            dfs(to,v);
            fup[v]=min(fup[v],fup[to]);
            if(fup[to]>=tin[v]){
                cutPoint[v]=(p!=-1);
                cnt++;
                ver[cnt].pb(v);
                g1[v].pb(cnt);
                g1[cnt].pb(v);
                while(ver[cnt].back()!=to){
                    g1[cnt].pb(st.top());
                    g1[st.top()].pb(cnt);
                    ver[cnt].pb(st.top());
                    st.pop();
                }
            }
        }
        else{
            fup[v]=min(fup[v],tin[to]);
        }
    }
    if(p==-1&&children>1){
        cutPoint[v]=1;
    }
}

int ans;
int zs[MAX];
int cur=0;

void calc(int v,int p=-1){
    zs[v]=(v<=n);
    use[v]=1;
    for(auto to:g1[v]){
        if(to==p)continue;
        calc(to,v);
        zs[v]+=zs[to];
        if(v>n){
            ans-=zs[to]*(zs[to]-1)*(sz(g1[v])-1);
        }
    }
    if(v>n){
        ans-=(cur-zs[v])*(cur-zs[v]-1)*(sz(g1[v])-1);
    }
}

void calc_sz(int v,int p=-1){
    cur+=(v<=n);
    for(auto to:g1[v]){
        if(to==p)continue;
        calc_sz(to,v);
    }
}

void bct(){
    cnt=n;
    for(int i=1;i<=n;i++){
        if(!use[i])dfs(i);
    }
    for(int i=1;i<=n;i++){
        // for(auto to:g1[i])cout<<i<<" "<<to<<"\n";
    }
    memset(use,0,sizeof(use));
    for(int i=1;i<=n;i++){
        if(!use[i]){
            cur=0;
            calc_sz(i);
            // cout<<cur<<"\n";
            ans+=cur*(cur-1)*(cur-2);
            calc(i);
        }
    }
}

void solve(){
    cin>>n>>m;
    for(int i=1;i<=m;i++){
        int a,b;
        cin>>a>>b;
        g[a].pb(b);
        g[b].pb(a);
    }
    bct();
    // cout<<n*(n-1)*(n-2)/3<<"\n";
    cout<<ans<<"\n";
}

signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t=1;
    // cin>>t;
    while(t--)solve();
}

• 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