Submission #733623

#	Time	Username	Problem	Language	Result	Execution time	Memory
733623		bin9638	Duathlon (APIO18_duathlon)	C++17	0 / 100	8 ms	9684 KiB

count_triplets

#include <bits/stdc++.h>

using namespace std;

#define N 200010
#define ll long long
#define fs first
#define sc second
#define ii pair<int,int>
#define pb push_back

int ans=0,times,num[N],low[N],n,m,ktr[N],dem,sz[N],child[N];
vector<int>g[N],edge[N];
stack<int>st;

void visit(int u,int p)
{
    num[u]=low[u]=++times;
    for(auto v:g[u])
        if(v!=p)
        {
            if(num[v]!=0)
            {
                low[u]=min(low[u],num[v]);
            }else
            {
                st.push(u);
                visit(v,u);
                low[u]=min(low[u],low[v]);
                if(low[v]>=num[u])
                {
                    int k;
                    dem++;
                    do{
                        k=st.top();
                        st.pop();

                        if(ktr[k]!=dem)
                        {
                             sz[dem]++;
                            ktr[k]=dem;
                            edge[dem].pb(k);
                            edge[k].pb(dem);
                        }
                    }while(k!=u);
                }
            }
        }
    st.push(u);
}

void build(int u,int p)
{
    child[u]=(u<=n);
    //cout<<u<<" "<<child[u]<<endl;
    for(auto v:edge[u])
        if(v!=p)
        {
            build(v,u);
            child[u]+=child[v];
        }
}

void DFS(int u,int p)
{
    if(u<=n)
    {
        int sum=n-1;
        for(auto v:edge[u])
            if(v!=p)
            {
                sum-=child[v];
                ans+=sum*child[v];
            //    cout<<sum<<" "<<child[v]<<endl;
            }
    }else
    {
        int sum=n;
        for(auto v:edge[u])
            if(v!=p)
            {
                sum-=child[v];
                ans+=sum*child[v]*(sz[u]-2);
               // cout<<u<<" "<<sum<<" "<<child[v]<<" "<<sz[u]<<endl;
            }
    }
    //cout<<u<<" "<<ans*2<<endl;
    for(auto v:edge[u])
        if(v!=p)
            DFS(v,u);
}

int32_t main()
{
    freopen("A.inp","r",stdin);
    freopen("A.out","w",stdout);
    ios::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);
    cin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        int u,v;
        cin>>u>>v;
        g[u].pb(v);
        g[v].pb(u);
    }
    dem=n;
    for(int i=1;i<=n;i++)
        if(num[i]==0)
            visit(i,0);
    //cout<<dem<<endl;
    build(1,0);
  // cout<<child[1]<<endl;
    DFS(1,0);
    cout<<ans*2;
    return 0;
}

Compilation message (stderr)

count_triplets.cpp: In function 'int32_t main()':
count_triplets.cpp:95:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   95 |     freopen("A.inp","r",stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~
count_triplets.cpp:96:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   96 |     freopen("A.out","w",stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 8
• Subtask 4: 0 / 10
• Subtask 5: 0 / 13
• Subtask 6: 0 / 15
• Subtask 7: 0 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10