Submission #3278333

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Source Code Expand

#include "bits/stdc++.h"

using namespace std;

typedef long long ll;
typedef pair<int,int> P;
constexpr double EPS = 1e-12;
constexpr int INF = numeric_limits<int>::max()/2;
constexpr int MOD = 1e9+7;

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

    int n;cin>>n;
    vector<P> v;
    for(int i=0;i<n;i++){
      ll a;cin>>a;
      v.push_back(P(a,0));
    }
    for(int i=0;i<n;i++){
      ll b;cin>>b;
      v.push_back(P(b,1));
    }
    sort(v.begin(),v.end());
    ll acnt=0,bcnt=0;
    ll res=1;
    for(int i=0;i<2*n;i++){
      if(v[i].second==0){
        if(bcnt){
          res *= bcnt;
          res %= MOD;
          bcnt--;
          continue;
        }
        acnt++;
      }
      else{
        if(acnt){
          res *= acnt;
          res %= MOD;
          acnt--;
          continue;
        }
        bcnt++;
      }
    }
    cout<<res<<endl;
}

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