Submission #954442

#	Time	Username	Problem	Language	Result	Execution time	Memory
954442		TAhmed33	Event Hopping (BOI22_events)	C++98	0 / 100	1586 ms	6628 KiB

events

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 25;
const int B = 18;
int dp[B][MAXN];
int n, q;
pair <int, int> a[MAXN];
int jump (int a, int b) {
	for (int i = B - 1; i >= 0; i--) {
		if (b & (1 << i)) {
			a = dp[i][a];
		}
	}
	return a;
}
int main () {
	ios::sync_with_stdio(0); cin.tie(0);
	cin >> n >> q;
	for (int i = 1; i <= n; i++) {
		cin >> a[i].first >> a[i].second;
	}
	for (int i = 1; i <= n; i++) {
		dp[0][i] = i;
		for (int j = 1; j <= n; j++) {
			if (a[j].second >= a[i].first && a[j].second <= a[i].second) {
				if (a[j].first < a[dp[0][i]].first) dp[0][i] = j;
			}
		}
	}
	for (int i = 1; i < B; i++) {
		for (int j = 1; j <= n; j++) {
			dp[i][j] = dp[i - 1][dp[i - 1][j]];
		}
	}
	while (q--) {
		int x, y; cin >> x >> y;
		if (x == y) {
			cout << "0\n";
			continue;
		}
		int ans = 0;
		if (a[y].first <= a[x].second) {
			ans = -1;
		} else {
			for (int i = B - 1; i >= 0; i--) {
				auto g = dp[i][y];
				if (!g) continue;
				if (a[g].first > a[x].second) {
					ans ^= 1 << i;
					y = g;
				}
			}
		}
		y = jump(y, 1);
		if (a[x].second <= a[y].second && a[x].second >= a[y].first) {
			cout << ans + 2 << '\n';
		} else {
			cout << "impossible\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