Submission #1280993

#	Time	Username	Problem	Language	Result	Execution time	Memory
1280993		quan606303	Railway (BOI17_railway)	C++20	100 / 100	141 ms	34700 KiB

railway

/*
 * @Author: RMQuan 
 * @Date: 2025-10-20 01:15:40 
 * @Last Modified by: RMQuan
 * @Last Modified time: 2025-10-20 02:31:53
 */
/*idea : 



*/
#include <bits/stdc++.h>
bool M1;
#define int long long
#define ll long long
#define INTMAX INT_MAX
#define INTMIN INT_MIN
#define LONGMAX LLONG_MAX
#define LONGMIN LLONG_MIN
#define fi first
#define se second
#define memfull(a,b) memset(a,b,sizeof(a));
#define endl '\n'
#define TASK "TEST"
#define file() if (fopen(TASK".inp","r")){freopen(TASK".inp","r",stdin); freopen(TASK".out","w",stdout);}
using namespace std;
const int MOD=1e9+7;
const int maxn=100005;
const int LOG=16;
int up[maxn][LOG+1],h[maxn];
vector<pair<int,int> > adj[maxn];
int n,m,k;
int tin[maxn],tout[maxn],id_dfs=0,dp[maxn];
void dfs(int u,int p)
{
    tin[u]=++id_dfs;
    for (auto v:adj[u])
    {
        if (v.fi==p)continue;
        h[v.fi]=h[u]+1;
        up[v.fi][0]=u;
        for (int i=1;i<=LOG;i++)up[v.fi][i]=up[up[v.fi][i-1]][i-1];
        dfs(v.fi,u);
    }
    tout[u]=id_dfs;
}
int lca(int u,int v)
{
    if (h[u]<h[v])swap(u,v);
    for (int i=LOG;i>=0;i--)if (h[up[u][i]]>=h[v])u=up[u][i];
    if (u==v)return u;
    for (int i=LOG;i>=0;i--)
    {
        if (up[u][i]!=up[v][i])
        {
            u=up[u][i];
            v=up[v][i];
        }
    }    
    return up[u][0];
}
bool cmp(int x,int y)
{
    return tin[x]<tin[y];
}
bool is_acestor(int x,int y)
{
    return tin[x]<=tin[y]&&tin[y]<=tout[x];
}
int build_virtualtree(vector<int> &vers)
{
    int N=vers.size();
    sort(vers.begin(),vers.end(),cmp);
    for (int i=1;i<N;i++)vers.push_back(lca(vers[i],vers[i-1]));
    sort(vers.begin(),vers.end(),cmp);
    vers.erase(unique(vers.begin(),vers.end()),vers.end());
    int root=vers[0];
    stack<int> st;
    st.push(root);
    for (int i=1;i<vers.size();i++)
    {
        while(st.size()&&!is_acestor(st.top(),vers[i]))st.pop();
        int u=st.top();
        int v=vers[i];
        dp[v]++;
        dp[u]--;
        st.push(v);
    }
    return root;
}
vector<int> ans;
void dfs_cal(int u,int p)
{
    for (auto v:adj[u])
    {
        if (v.fi==p)continue;
        dfs_cal(v.fi,u);
        if (dp[v.fi]>=k)ans.push_back(v.se);
        dp[u]+=dp[v.fi];
    }
}
int32_t main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    file();
    cin>>n>>m>>k;
    for (int i=1;i<n;i++)
    {
        int x,y;
        cin>>x>>y;
        adj[x].push_back({y,i});
        adj[y].push_back({x,i});
    }
    h[0]=-1;
    dfs(1,0);
    while(m--)
    {
        int k;
        cin>>k;
        vector<int> vers;
        for (int i=1;i<=k;i++)
        {
            int x;
            cin>>x;
            vers.push_back(x);
        }
        int root=build_virtualtree(vers);
    }
    dfs_cal(1,0);
    sort(ans.begin(),ans.end());
    cout<<ans.size()<<endl;
    for (auto i:ans)cout<<i<<" ";
    bool M2;
    cerr<<"-------------------------------------------------"<<endl;
    cerr<<"Time : "<<clock()<<" ms"<<endl;
    cerr<<"Memory : "<<abs(&M2-&M1)/1024/1024<<" MB"<<endl;
    cerr<<"-------------------------------------------------"<<endl;
    return 0;
}

Compilation message (stderr)

railway.cpp: In function 'int32_t main()':
railway.cpp:25:50: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   25 | #define file() if (fopen(TASK".inp","r")){freopen(TASK".inp","r",stdin); freopen(TASK".out","w",stdout);}
      |                                           ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
railway.cpp:107:5: note: in expansion of macro 'file'
  107 |     file();
      |     ^~~~
railway.cpp:25:81: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   25 | #define file() if (fopen(TASK".inp","r")){freopen(TASK".inp","r",stdin); freopen(TASK".out","w",stdout);}
      |                                                                          ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:107:5: note: in expansion of macro 'file'
  107 |     file();
      |     ^~~~

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 7 / 7
• Subtask 4: 29 / 29
• Subtask 5: 16 / 16
• Subtask 6: 25 / 25