제출 #601031

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
601031		CSQ31	Event Hopping (BOI22_events)	C++17	25 / 100	1594 ms	4652 KiB

events

#include <bits/stdc++.h>
using namespace std;
#define all(a) a.begin(),a.end()
#define owo ios_base::sync_with_stdio(0);cin.tie(0);
const int MAXN = 1e5+1;
int s[MAXN],e[MAXN];
int main()
{
	owo
	int n,q;
	cin>>n>>q;
	vector<int>crd;
	for(int i=0;i<n;i++)cin>>s[i]>>e[i];
	for(int i=0;i<n;i++){
		crd.push_back(s[i]);
		crd.push_back(e[i]);
	}
	sort(all(crd));
	crd.resize(unique(all(crd)) - crd.begin());
	for(int i=0;i<n;i++){
		s[i] = lower_bound(all(crd),s[i]) - crd.begin()+1;
		e[i] = lower_bound(all(crd),e[i]) - crd.begin()+1;
	}
	int m = crd.size();
	vector<int>mn(m+1);
	for(int i=1;i<=m;i++)mn[i] = i;
	for(int i=0;i<n;i++){
		mn[e[i]] = min(mn[e[i]],s[i]);
		
	}
	//cout<<"range"<<'\n';
	//for(int i=0;i<n;i++)cout<<s[i]<<" "<<e[i]<<'\n';
	//for(int i=1;i<=m;i++)cout<<mn[i]<<" ";
	//cout<<'\n';
	
	//greedy backwards
	//forward fails because we are going to exact nodes
	while(q--){
		int l,r;
		cin>>l>>r;
		l--;
		r--;
		if(l==r){
			cout<<0<<'\n';
			continue;
		}
		if(e[l] > e[r]){
			cout<<"impossible"<<'\n';
			continue;
		}
		int cur = s[r];
		int last = e[r];
		int ans = 1;
		while(cur > e[l]){
			int best = cur;
			for(int i=cur;i<=last;i++)best = min(best,mn[i]);
			if(best == cur){
				ans = -1;
				break;
			}
			last = cur;
			cur = best;
			ans++;
		}
		if(ans==-1)cout<<"impossible"<<'\n';
		else cout<<ans<<'\n';
	}
	
	
}

• Subtask 1: 0 / 10
• Subtask 2: 10 / 10
• Subtask 3: 0 / 15
• Subtask 4: 15 / 15
• Subtask 5: 0 / 20
• Subtask 6: 0 / 30