Submission #2172606

---

Source Code Expand

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

#define INF 1.1e9
#define LINF 1.1e18
#define FOR(i,a,b) for (int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
#define pb push_back
#define pf push_front
#define fi first
#define se second
#define BIT(x,n) bitset<n>(x)
#define PI 3.14159265358979323846

typedef long long ll;
typedef pair<int,int> P;
//typedef pair<int,P> PP;

//-----------------------------------------------------------------------------

int n,tmp;
vector<P> vec;
const int MOD=1e9+7;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	cin>>n;
	REP(i,2*n) {
		cin>>tmp;
		vec.pb(P(tmp,(int)(i>=n)));
	}
	sort(ALL(vec));
	ll ans=1;
	int cnt_a=0,cnt_b=0;
	for(auto v:vec) {
		if(v.se==0) {
			if(cnt_b==0) cnt_a++;
			else (ans*=cnt_b)%=MOD,cnt_b--;
		}
		if(v.se==1) {
			if(cnt_a==0) cnt_b++;
			else (ans*=cnt_a)%=MOD,cnt_a--;
		}
		//cout<<cnt_a<<' '<<cnt_b<<' '<<ans<<endl;
	}
	cout<<ans<<endl;

	return 0;
}

Submission Info

Judge Result