Submission #1326737

#	Time	Username	Problem	Language	Result	Execution time	Memory
1326737		yus1f_m	Railway (BOI17_railway)	C++20	100 / 100	131 ms	40232 KiB

railway

#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#define ll long long
#define str string
#define pb push_back
#define pf push_front
#define in insert
#define all(v) v.begin(),v.end()
const int sz=100001,INF=1000000000;
using namespace std;
ll n,m,l,num1,num2,num,Num,t;
vector<ll>Nums,idxs(sz),d(sz),tin(sz),Parent(sz),res(sz),ans;
vector<bool>isSeen(sz),isSeen1(sz),isSeen2(sz);
vector<vector<ll>>parent(sz,vector<ll>(21));
vector<vector<pair<ll,ll>>>nums;
void dfs1(ll num1,ll num2)
{
    isSeen1[num1]=true,tin[num1]=t,t++,idxs[num1]=num2;
    for(int i=0;i<nums[num1].size();i++)
    {
        if(!isSeen1[nums[num1][i].first])
        {
            parent[nums[num1][i].first][0]=num1,d[nums[num1][i].first]=d[num1]+1,Parent[nums[num1][i].first]=num1;
            dfs1(nums[num1][i].first,nums[num1][i].second);
        }
    }
}
void dfs2(ll num)
{
    isSeen2[num]=true;
    for(int i=0;i<nums[num].size();i++)
    {
        if(!isSeen2[nums[num][i].first])
        {
            dfs2(nums[num][i].first);
            res[num]+=res[nums[num][i].first];
        }
    }
}
ll lca(ll num1,ll num2)
{
    if(d[num1]<d[num2])
    {
        swap(num1,num2);
    }
    for(int i=20;i>=0;i--)
    {
        if(d[num1]-pow(2,i)>=d[num2])
        {
            num1=parent[num1][i];
        }
    }
    if(num1==num2)
    {
        return num1;
    }
    else
    {
        for(int i=20;i>=0;i--)
        {
            if(parent[num1][i]!=parent[num2][i])
            {
                num1=parent[num1][i],num2=parent[num2][i];
            }
        }
        return parent[num1][0];
    }
}
bool comp(ll num1,ll num2)
{
    if(tin[num1]<tin[num2])
    {
        return true;
    }
    else
    {
        return false;
    }
}
void solve()
{
    cin>>n>>m>>l;
    nums.resize(n+1);
    for(int i=0;i<n-1;i++)
    {
        cin>>num1>>num2;
        nums[num1].pb({num2,i+1}),nums[num2].pb({num1,i+1});
    }
    dfs1(1,0);
    for(int i=1;i<=20;i++)
    {
        for(int j=1;j<=n;j++)
        {
            parent[j][i]=parent[parent[j][i-1]][i-1];
        }
    }
    for(int i=0;i<m;i++)
    {
        Nums.clear();
        cin>>num;
        for(int j=0;j<num;j++)
        {
            cin>>Num;
            Nums.pb(Num);
        }
        sort(all(Nums),comp);
        for(int j=0;j<Nums.size();j++)
        {
            res[Nums[j]]++,res[Nums[(j+1)%num]]++,res[lca(Nums[j],Nums[(j+1)%num])]-=2;
        }
    }
    dfs2(1);
    for(int i=1;i<=n;i++)
    {
        for(int j=0;j<nums[i].size();j++)
        {
            if(!isSeen[idxs[nums[i][j].first]] && res[nums[i][j].first]>=2*l)
            {
                ans.pb(idxs[nums[i][j].first]),isSeen[idxs[nums[i][j].first]]=true;
            }
        }
    }
    cout<<ans.size()<<"\n";
    for(int i=0;i<ans.size();i++)
    {
        cout<<ans[i]<<" ";
    }
}
int main()
{   
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr),cout.tie(nullptr);
    ll t=1;
    //cin>>t;
    while(t--)
    {
        solve();
    }
}

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