Submission #710568

#	Time	Username	Problem	Language	Result	Execution time	Memory
710568		lam	Duathlon (APIO18_duathlon)	C++14	100 / 100	143 ms	36704 KiB

count_triplets

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int maxn = 3e5 + 10;
int n,m,ans;
vector <int> adj[maxn],adj2[maxn];
stack <int> st;
int l[maxn],t[maxn],cnt,sl,bcc,s[maxn];
void dfs(int x, int p)
{
    l[x] = t[x] = ++cnt; sl++;
    st.push(x);
    for (int i:adj[x])
        if (i!=p)
    {
        if (t[i]==0)
        {
            dfs(i,x);
            l[x]=min(l[x],l[i]);
            if (l[i]>=t[x])
            {
                bcc++;
//                cout<<bcc+n<<' '<<st.size()<<" := "<<x<<' ';
                adj2[x].push_back(bcc + n);
                int temp;
                do
                {
                    temp = st.top(); st.pop();
//                    cout<<temp<<" , ";
                    adj2[bcc+n].push_back(temp);
                }
                while (temp!=i);
//                cout<<endl;
            }
        }
        else l[x] = min(l[x],t[i]);
    }
//    cout<<x<<" :: "<<l[x]<<' '<<t[x]<<endl;
}
void dfs2(int x, int p)
{
    s[x] = (x<=n);
//    cout<<x<<" !! "<<endl;
    for (int i:adj2[x])
        if (i!=p)
    {
        dfs2(i,x);
        s[x]+=s[i];
        if (x>n)
        {
            ans -= 1LL*((int)adj2[x].size()) * s[i] * (s[i]-1);
        }
    }
//    cout<<x<<' '<<sl<<" -> "<<s[x]<<' '<<(int)adj[x].size()<<endl;
    if (x>n) ans -= 1LL* (sl - s[x]) * (sl - s[x] - 1) * (int)adj2[x].size();
}
signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);
    cin>>n>>m;
    for (int i=1; i<=m; i++)
    {
        int u,v; cin>>u>>v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    cnt = bcc = sl = 0;
    for (int i=1; i<=n; i++)
    {
        if (t[i]) continue;
        sl=0;
        dfs(i,i);
        ans += sl*(sl-1)*(sl-2);
        dfs2(i,i);
    }
    cout<<ans<<'\n';
}

• 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