Submission #1162001

#	Time	Username	Problem	Language	Result	Execution time	Memory
1162001		son2008	Railway (BOI17_railway)	C++20	100 / 100	143 ms	50372 KiB

railway

#include<bits/stdc++.h>
using namespace std;
#define task "task"
#define ii pair<int,int>
#define fi first
#define se second
//#define int long long
#define ll long long
#define ld double
#define mp make_pair
#define lg2 30
#define iii pair<int,ii>
#define iiii pair<ii,ii>
#define base 29
#define eps 1e-8
int dx[]= {0LL,0LL,1,-1,1,1,-1,-1};
int dy[]= {1,-1,0LL,0LL,1,-1,1,-1};
const int maxn=1e5+5;
const int mod=1e9+7;
int n,m,k,P[maxn][lg2+1],h[maxn],thanh[maxn];
ii b[maxn];
vector<int>a[maxn],luu[maxn],ans;
set<int>st[maxn];
void pre(int u,int cha)
{
    for(int v:a[u])
    {
        if(v==cha)continue;
        P[v][0]=u;
        h[v]=h[u]+1;
        pre(v,u);
    }
}
void build_lca()
{
    for(int j=1; j<=lg2; j++)
    {
        for(int i=1; i<=n; i++)
            P[i][j]=P[P[i][j-1]][j-1];
    }
}
int lca(int u,int v)
{
    if(h[u]<h[v])swap(u,v);
    for(int i=lg2; i>=0; i--)
    {
        if(h[u]-h[v]>=(1<<i))
            u=P[u][i];
    }
    if(u==v)
    {
        return u;
    }
    for(int i=lg2; i>=0; i--)
    {
        if(P[u][i]!=P[v][i])
        {
            u=P[u][i];
            v=P[v][i];
        }
    }
    return P[u][0];
}
void init()
{
    cin>>n>>m>>k;
    for(int i=1;i<n;i++)
    {
        int u,v;
        cin>>u>>v;
        b[i]={u,v};
        a[u].push_back(v);
        a[v].push_back(u);
    }
    pre(1,-1);
    build_lca();
    for(int i=1;i<n;i++)
    {
        if(h[b[i].fi]>h[b[i].se])thanh[b[i].fi]=i;
        else thanh[b[i].se]=i;
    }
}
void dfs(int u,int cha)
{
    for(int v:a[u])
    {
        if(v==cha)continue;
        dfs(v,u);
        if(st[v].size()>=k)ans.push_back(thanh[v]);
        if(st[u].size()<st[v].size())swap(st[u],st[v]);
        for(int x:st[v])st[u].insert(x);
    }
    for(int x:luu[u])
    {
        if(st[u].find(x)!=st[u].end())st[u].erase(x);
    }
}
void process()
{
    for(int i=1;i<=m;i++)
    {
        int s,lc=0;
        cin>>s;
        for(int j=1;j<=s;j++)
        {
            int x;
            cin>>x;
            if(!lc)lc=x;
            else lc=lca(lc,x);
            st[x].insert(i);
        }
        luu[lc].push_back(i);
    }
    dfs(1,-1);
    sort(ans.begin(),ans.end());
    cout<<ans.size()<<'\n';
    for(int x:ans)cout<<x<<" ";
}
signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    if(fopen(task".inp","r"))
    {
        freopen(task".inp","r",stdin);
        freopen(task".out","w",stdout);
    }
    init();
    process();
    cerr <<endl<< "TIME : " << clock() * 0.001 << "s" << endl ;
}

Compilation message (stderr)

railway.cpp: In function 'int main()':
railway.cpp:126:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  126 |         freopen(task".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
railway.cpp:127:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  127 |         freopen(task".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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