Submission #1908476

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Source Code Expand

#include <cmath>
#include <stack>
#include <iostream>
#include <algorithm>
using namespace std;
int n, a[100009], b[100009], p[200009]; bool vis[100009];
int main() {
	cin >> n;
	for (int i = 0; i < n; i++) cin >> a[i];
	for (int i = 0; i < n; i++) cin >> b[i];
	for (int i = 0; i < 2 * n; i++) p[i] = i;
	sort(p, p + 2 * n, [](int v1, int v2) { return (v1 < n ? a[v1] : b[v1 - n]) < (v2 < n ? a[v2] : b[v2 - n]); });
	int ret = 1, d = 0;
	stack<int> s;
	for (int i = 0; i < 2 * n; i++) {
		d += (p[i] < n ? 1 : -1);
		if ((d > 0 && p[i] < n) || (d < 0 && p[i] >= n)) {
			s.push(i);
		}
		else {
			ret = 1LL * ret * (i - s.top() + 1) / 2 % 1000000007;
			s.pop();
		}
	}
	cout << ret << endl;
	return 0;
}

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