Submission #1246280

#	Time	Username	Problem	Language	Result	Execution time	Memory
1246280		trideser	Event Hopping (BOI22_events)	C++20	0 / 100	1595 ms	1352 KiB

events

#include <bits/stdc++.h>
using namespace std;

int main() {
	int N, Q;
	cin >> N >> Q;
	vector<pair<int, int>> events(N);
	for(int i = 0; i < N; i++) {
		int a, b;
		cin >> a >> b;
		events[i] = make_pair(a, b);
	}
	//vector<pair<int, int>> events2 = events;
	//sort(events2.begin(), events2.end());
	vector<int> optimal(N);
	for(int i = 0; i < N; i++) {
		int opt = -1;
		for(int j = 0; j < N; j++) {
			//cout << events[i].first << " - " << events[i].second << " : ";
			//cout << events[j].first << " - " << events[j].second << "\n";
			//cout << (events[j].first < events[i].first) << (events[j].second > events[i].first) << "\n";
			if(events[j].first < events[i].first &&
					events[j].second >= events[i].first &&
					events[j].second <= events[i].second &&
					(opt == -1 || events[j].first < events[opt].first)) {
				//cout << "OPT\n";
				opt = j;
			}
		}

		optimal[i] = opt;
	}
	vector<vector<int>> jumps;
	jumps.push_back(optimal);
	bool bb = true;
	while(bb) {
		bb = false;
		vector<int> cur(N);
		for(int i = 0; i < N; i++) {
			if(jumps.back()[i] == -1)
				cur[i] = -1;
			else{
				cur[i] = jumps.back()[jumps.back()[i]];
				bb = true;
			}
		}
		jumps.push_back(cur);
	}
	/*for(vector<int> vec : jumps) {
		for(int a : vec)
			cout << a << " ";
		cout << "\n";
	}*/
	for(int i = 0; i < Q; i++) {
		int a, b;
		cin >> a >> b;
		if(a == b) {
			cout << "0\n";
			continue;
		}
		a--;
		b--;
		if(events[a].second > events[b].second) {
			cout << "impossible\n";
			continue;
		}
		int ret = 0;
		int currentE = b;
		bool possible = false;
		/*while(currentE != -1 && events[currentE].first > events[a].second) {
			//cout << "\t" << currentE << "\n";
			currentE = optimal[currentE];
			ret++;
		}*/
		
		for(int i = jumps.size() - 1; i >= 0; i--) {
			if(jumps[i][currentE] == -1)
				continue;
			if(events[jumps[i][currentE]].first > events[a].second) {
				currentE = jumps[i][currentE];
				ret += (1 << i);
			}
			else {
				possible = true;
			}
		}
		if(!possible)
			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