Submission #791902

#	Time	Username	Problem	Language	Result	Execution time	Memory
791902		ToniB	Event Hopping (BOI22_events)	C++17	0 / 100	384 ms	26656 KiB

events

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 2e5 + 2;
const int LOG = 17;

int n, q, s[MAXN], e[MAXN], bl[MAXN][LOG];
set<pair<int, int> > st;
vector<pair<int, bool> > v[MAXN];

int main(){
	cin >> n >> q;
	unordered_map<int, int> um;
	vector<int> cmp;
	for(int i = 0; i < n; ++i){
		cin >> s[i] >> e[i];
		cmp.push_back(s[i]);
		cmp.push_back(e[i]);
	}
	sort(cmp.begin(), cmp.end());
	cmp.erase(unique(cmp.begin(), cmp.end()), cmp.end());
	for(int i = 0; i < (int)cmp.size(); ++i){
		um[cmp[i]] = i;
	}
	for(int i = 0; i < n; ++i){
		s[i] = um[s[i]]; e[i] = um[e[i]];
		v[s[i]].push_back({i, 0});
		v[e[i]].push_back({i, 1});
	}
	for(int i = 0; i < 2*n; ++i){
		for(pair<int, bool> p : v[i]){
			if(!p.second){
				st.insert({e[p.first], p.first});
			}
		}
		for(pair<int, bool> p : v[i]){
			if(p.second){
				int idx = (*--st.end()).second;
				bl[p.first][0] = idx;
			}
		}
	}
	for(int j = 1; j < LOG; ++j){
		for(int i = 0; i < n; ++i){
			bl[i][j] = bl[bl[i][j - 1]][j - 1];
		}
	}
	while(q--){
		int qs, qe; cin >> qs >> qe, --qs, --qe;
		if(qs == qe){
			cout << "0\n"; continue;
		} else if(s[qs] <= s[qe] && s[qe] <= e[qs]){
			cout << "1\n"; continue;
		} else if(e[qs] > e[qe]){
			cout << "impossible\n"; continue;
		}

		int ret = 0;
		for(int i = LOG - 1; i >= 0; --i){
			int idx = bl[qs][i];
			if(e[idx] < s[qe]){
				qs = idx;
				ret += 1 << i;
			}
		}
		if(e[bl[qs][0]] < s[qe]) cout << "impossible\n";
		else if(bl[qs][0] != qe) cout << "impossible\n";
		else cout << ret + 2 << "\n";
	}
	return 0;
}

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