Submission #600994

#	Time	Username	Problem	Language	Result	Execution time	Memory
600994		CSQ31	Event Hopping (BOI22_events)	C++17	10 / 100	1572 ms	4104 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];
bool check(int x,int j){ //got edge i->j?
	return s[j] <= x && x <= e[j];
}
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();
		e[i] = lower_bound(all(crd),e[i]) - crd.begin();
	}
	int m = crd.size();

	//greedy : always jump to the rightmost guy with e < e[r]
	while(q--){
		int l,r;
		cin>>l>>r;
		l--;
		r--;
		int ans = 0;
		if(l==r){
			cout<<0<<'\n';
			continue;
		}
		int i = e[l];
		while(true){
			if(check(i,r)){
				ans++;
				break;
			}
			int k = i;
			for(int j=0;j<n;j++){
				if(check(i,j) && e[j] <= e[r])k = max(e[j],k);	
			}
			if(k==i){
				ans=-1;
				break;
			}
			ans++;
			i = k;
		}
		if(ans==-1)cout<<"impossible"<<'\n';
		else cout<<ans<<'\n';
	}
	
	
}

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:27:6: warning: unused variable 'm' [-Wunused-variable]
   27 |  int m = crd.size();
      |      ^

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