Submission #960785

#	Time	Username	Problem	Language	Result	Execution time	Memory
960785		Trisanu_Das	Event Hopping (BOI22_events)	C++17	100 / 100	116 ms	13396 KiB

events

#include <bits/stdc++.h>
using namespace std;
 
const int N = 1e5 + 10 , L = 18;
int n , q , l[N] , r[N] , mv[L][N];
vector <int> vec , st;
 
bool cmp(int a , int b) {
	if(r[a] != r[b]) return r[a] < r[b];
	return l[a] < l[b];
}
 
int Bs(int x){
	int low = -1 , high = st.size();
	while(high - low > 1) {
		int mid = (low + high) >> 1;
		if(r[st[mid]] >= x) high = mid;
		else low = mid;
	}
	return st[high];
}
 
int solve(int from , int to , int bit) {
	if(bit == -1) return 0;
	int nex = mv[bit][from];
	if(l[nex] > r[to]) return (1 << bit) + solve(nex , to , bit - 1);
	return solve(from , to , bit - 1);
}
 
signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);  cout.tie(0);
	cin >> n >> q;
	for(int i = 1 ; i <= n ; i++) {
		cin >> l[i] >> r[i];
		vec.push_back(i);
	}
	sort(vec.begin() , vec.end() , cmp);
	for(int i = 1 ; i <= n ; i++) {
		int now = vec[i];
		while(!st.empty() && l[st.back()] >= l[now]) st.pop_back();
		st.push_back(now);
		mv[0][now] = Bs(l[now]);
	}
	for(int i = 1 ; i < L ; i++)   for(int j = 1 ; j <= n ; j++) mv[i][j] = mv[i - 1][mv[i - 1][j]];
	while(q--) {
		int s , e;  cin >> s >> e;
		if(l[mv[L - 1][e]] > r[s] || r[e] < r[s]) {
			cout << "impossible" << '\n';
			continue;
		}
		if(s == e) {
			cout << 0 << '\n';
			continue;
		}
		if(l[e] <= r[s]) {
			cout << 1 << '\n';
			continue;
		}
		cout << solve(e , s , L - 1) + 2 << '\n';
	}
}

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