Submission #1226906

#	Time	Username	Problem	Language	Result	Execution time	Memory
1226906		wedonttalkanymore	Event Hopping (BOI22_events)	C++20	100 / 100	137 ms	19212 KiB

events

#include <bits/stdc++.h>
using namespace std;
#define pii pair <int, int>
#define fi first
#define se second
const int lim = 20;
int n, q;
int left1[100005], right1[100005], up[100005][21];
vector <int> comp;
pii st[1000005];
void update(int i, int l, int r, int pos, pii val)
{
	if (l == r)
	{
		st[i] = min(st[i], val);
		return;
	}
	int mid = (l + r) / 2;
	if (pos <= mid) update(2 * i, l, mid, pos, val);
	else update(2 * i + 1, mid + 1, r, pos, val);
	st[i] = min(st[2 * i], st[2 * i + 1]);
}
pii get(int i, int l, int r, int u, int v)
{
	if (u > r || v < l) return {1e9, 1e9};
	if (u <= l && r <= v) return st[i];
	int mid = (l + r) / 2;
	return min(get(2 * i, l, mid, u, v), get(2 * i + 1, mid + 1, r, u, v));
}
signed main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	cin >> n >> q;
	for (int i = 1; i <= n; i++)
	{
		cin >> left1[i] >> right1[i];
		comp.push_back(left1[i]);
		comp.push_back(right1[i]);
	}
	sort(comp.begin(), comp.end());
	comp.erase(unique(comp.begin(), comp.end()), comp.end());
	int x = comp.size();
	memset(st, 0x3f, sizeof(st));
	for (int i = 1; i <= n; i++)
	{
		auto it = lower_bound(comp.begin(), comp.end(), right1[i]) - comp.begin() + 1;
		update(1, 1, x, it, {left1[i], i});
	}
	for (int i = 1; i <= n; i++)
	{
		auto it = lower_bound(comp.begin(), comp.end(), left1[i]) - comp.begin() + 1;
		auto it1 = lower_bound(comp.begin(), comp.end(), right1[i]) - comp.begin() + 1;
		up[i][0] = get(1, 1, x, it, it1).se;
	}
	for (int i = 1; i <= lim; i++)
	{
		for (int u = 1; u <= n; u++)
		{
			up[u][i] = up[up[u][i - 1]][i - 1];
		}
	}
	for (int i = 1; i <= q; i++)
	{
		int l, r;
		cin >> l >> r;
		if (l == r)
		{
			cout << 0 << '\n';
			continue;
		}
		if (right1[l] > right1[r])
		{
			cout << "impossible" << '\n';
			continue;
		}
		if (left1[r] <= right1[l] && right1[l] <= right1[r])
		{
			cout << 1 << '\n';
			continue;
		}
		int ans = 2;
		for (int p = lim; p >= 0; p--)
		{
			if (left1[up[r][p]] > right1[l])
			{
				ans += (1 << p);
				r = up[r][p];
			}
		}
		r = up[r][0];
		if (left1[r] > right1[l])
		{
			cout << "impossible" << '\n';
			continue;
		}
		cout << ans << '\n';
	}
	return 0;
}

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