Submission #660109

#	Time	Username	Problem	Language	Result	Execution time	Memory
660109		Karuk	Event Hopping (BOI22_events)	C++14	100 / 100	262 ms	34072 KiB

events

#include<bits/stdc++.h>
#define endl '\n'
using namespace std;
pair<int,int>max(pair<int,int>a,pair<int,int>b) {
    return a.first>b.first?a:b;
}
const int k=(1<<20);
pair<int,int>maxv[k*2+1];
void upd(int x,int va,int ind) {
    pair<int,int>val={va,ind};
    while(x>0) {
        maxv[x]=max(maxv[x],val);
        x>>=1;
    }
}
pair<int,int> ask(int &from,int &to,int cur=1,int beg=0,int en=k-1) {
    if(from<=beg && en<=to)return maxv[cur];
    if(to<beg || en<from)return {-1,-1};
    int mid=(beg+en)>>1;
    return max(ask(from,to,cur<<1,beg,mid),ask(from,to,(cur<<1)|1,mid+1,en));
}
int main() {
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int n,q;cin>>n>>q;
    pair<int,int>a[n];
    vector<int>v;
    for(int i=0;i<n;i++) {
        int x,y;
        cin>>x>>y;
        v.push_back(x);
        v.push_back(y);
        a[i]={x,y};
    }
    sort(v.begin(),v.end());
    map<int,int>m;
    for(int i=0;i<v.size();i++)m[v[i]]=i;
    for(int i=0;i<n;i++) {
        int x,y;
        a[i].first=m[a[i].first];
        a[i].second=m[a[i].second];
        x=a[i].first;
        y=a[i].second;
        upd(y+k,k-x,i);
    }
    pair<int,int> prev[n][20];
    for(int i=0;i<n;i++) {
        pair<int,int>d=ask(a[i].first,a[i].second);
        d.first=k-d.first;
        prev[i][0]=d;
    }
    for(int j=1;j<20;j++) {
        for(int i=0;i<n;i++) {
            prev[i][j]=prev[prev[i][j-1].second][j-1];
        }
    }
    for(int i=0;i<q;i++) {
        int x,y;cin>>x>>y;x--;y--;
        if(x==y)cout<<0<<endl;
        else if(a[x].second>=a[y].first && a[x].second<=a[y].second)cout<<1<<endl;
        else if(a[x].second>a[y].second){cout<<"impossible"<<endl;}
        else {
            int cnt=0;
            int cur=y;
            int en=a[x].second;
            for(int j=19;j>=0;j--) {
                if(prev[cur][j].first>en) {
                    cur=prev[cur][j].second;
                    cnt+=(1<<j);
                }
            }
            if(prev[cur][0].first>en)cout<<"impossible"<<endl;
            else cout<<cnt+2<<endl;
        }
    }
    return 0;
}
///9:30

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:36:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   36 |     for(int i=0;i<v.size();i++)m[v[i]]=i;
      |                 ~^~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 15 / 15
• Subtask 4: 15 / 15
• Subtask 5: 20 / 20
• Subtask 6: 30 / 30