Submission #300769

#	Time	Username	Problem	Language	Result	Execution time	Memory
300769		vipghn2003	Ball Machine (BOI13_ballmachine)	C++14	100 / 100	282 ms	32380 KiB

ballmachine

#include<bits/stdc++.h>
#define fi first
#define se second
#define pii pair<int,int>
#define mp make_pair
using namespace std;

const int N=1e5+5;
int n,q,mn[N],pos[N],cnt,col[N],p[N][20];
vector<int>adj[N];

void dfs(int u,int par=-1)
{
    for(int i=1;i<=18;i++) p[u][i]=p[p[u][i-1]][i-1];
    mn[u]=u;
    for(auto&v:adj[u])
    {
        if(v==par) continue;
        p[v][0]=u;
        dfs(v,u);
        mn[u]=min(mn[u],mn[v]);
    }
}

void go(int u,int par=-1)
{
    vector<pii>order;
    for(auto&v:adj[u]) if(v!=par) order.push_back(mp(mn[v],v));
    sort(order.begin(),order.end());
    for(auto&v:order) go(v.se,u);
    pos[u]=++cnt;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cin>>n>>q;
    int root;
    for(int i=1;i<=n;i++)
    {
        int p;
        cin>>p;
        if(!p) root=i;
        else adj[p].push_back(i);
    }
    dfs(root);
    go(root);
    set<pii>empty_node;
    for(int i=1;i<=n;i++) empty_node.insert(mp(pos[i],i));
    while(q--)
    {
        int type,x;
        cin>>type>>x;
        int res=0;
        if(type==1)
        {
            while(x--)
            {
                auto it=empty_node.begin();
                res=(*it).se;
                col[res]=1;
                empty_node.erase(it);
            }
            cout<<res<<'\n';
            continue;
        }
        for(int i=18;i>=0;i--)
        {
            if(col[p[x][i]]==1)
            {
                res+=(1<<i);
                x=p[x][i];
            }
        }
        empty_node.insert(mp(pos[x],x));
        col[x]=0;
        cout<<res<<'\n';
    }
}

Compilation message (stderr)

ballmachine.cpp: In function 'int main()':
ballmachine.cpp:48:7: warning: 'root' may be used uninitialized in this function [-Wmaybe-uninitialized]
   48 |     go(root);
      |     ~~^~~~~~

• Subtask 1: 25 / 25
• Subtask 2: 30 / 30
• Subtask 3: 40 / 40
• Subtask 4: 5 / 5