Submission #1000618

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Source Code Expand

/* ***************************************
Author        :Scau.ion
Created Time  :2016/11/28 11:04:36 UTC+8
File Name     :ion.cpp
*************************************** */

#include <bits/stdc++.h>

#define LL long long
#define ULL unsigned long long
#define PB push_back
#define MP make_pair
#define PII pair<int,int>
#define VI vector<int>
#define VPII vector<PII>
#define X first
#define Y second
#define IOS ios::sync_with_stdio(0);cin.tie(0);
#define IN freopen("in", "r", stdin);
#define OUT freopen("out", "w", stdout);

using namespace std;

const int maxn=100010;
const int mod=1e9+7;

struct num
{
    int x;
    bool type;
    bool operator <(const num &b)const
    {
        return x<b.x;
    }
}ab[maxn*2];

int main()
{
    IOS;
    int n;
    cin>>n;
    int nn=n*2;
    for (int j=1;j<=nn;++j)
    {
        cin>>ab[j].x;
        ab[j].type=(j>n);
    }
    sort(ab+1,ab+n*2+1);
    LL ans=1;
    int sum=0;
    for (int j=1;j<=nn;++j)
    {
        int add;
        if (ab[j].type) add=1;
        else add=-1;
        if (!((sum<=0&&add<0)||(sum>=0&&add>0))) ans=ans*abs(sum)%mod;
        sum+=add;
    }
    cout<<ans<<endl;
    return 0;
}

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