Submission #745893

#	Time	Username	Problem	Language	Result	Execution time	Memory
745893		vjudge1	Event Hopping (BOI22_events)	C++17	0 / 100	113 ms	10772 KiB

events

#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
using namespace std;

struct event {
	int st, en, id;
};

const int maxn = 100010;
int nxt[maxn][20];

int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, q;
	cin >> n >> q;
	vector<event> e(n+1);
	for (int i = 1; i <= n; i++) {
		cin >> e[i].st >> e[i].en;
		e[i].id = i;
	}
	e.push_back({ (int)1e9+1, (int)1e9 + 1 });
	for (int i = 0; i < 20; i++) {
		nxt[n + 1][i] = n + 1;
	}
	vector<int> pos(n + 1);
	sort(e.begin()+1, e.end(), [](event& a, event& b) {return a.en < b.en; });
	int mn = n + 1;
	for (int i = n; i > 0; i--) {
		pos[e[i].id] = i;
		/*int l = i, r = n + 2;
		while (l + 1 < r) {
			int m = (l + r) / 2;
			if (e[m].st <= e[i].en)l = m;
			else r = m;
		}*/
		nxt[i][0] = (e[mn].st <= e[i].en ? mn : i);
		for (int j = 1; j < 20; j++) {
			nxt[i][j] = nxt[nxt[i][j - 1]][j - 1];
		}
		if (e[i].st < e[mn].st)mn = i;
	}
	for (int i = 0; i < q; i++) {
		int s, e;
		cin >> s >> e;
		s = pos[s];
		e = pos[e];
		if (e == s) {
			cout << "0\n";
			continue;
		}
		if (e < s) {
			cout << "impossible\n";
			continue;
		}
		int ans = 0;
		for (int i = 19; i >= 0; i--) {
			if (nxt[s][i] < e) {
				ans += (1 << i);
				s = nxt[s][i];
			}
		}
		if (nxt[s][0] != e) {
			cout << "impossible\n";
			continue;
		}
		cout << ans + 1 << '\n';
	}
}

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