Submission #3237251

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Source Code Expand

#include <bits/stdc++.h>
#define FOR(i, a, b) for(int i=(int)(a); i!=(int)(b); i++)
#define RFOR(i, a, b) for(int i=(int)(a); i!=(int)(b); i--)
#define REP(i, n) FOR(i, 0, n)
using namespace std;
using ll = long long;

constexpr int mod = 1e9+7;

int main(){
  int n; cin >> n;
  int a[n], b[n];
  pair<int, int> c[2*n];
  REP(i, n){
    cin >> a[i];
    c[i] = {a[i], 0};
  }
  REP(i, n){
    cin >> b[i];
    c[i+n] = {b[i], 1};
  }

  sort(c, c+2*n);

  ll ans = 1, com = 0, ele = 0;
  REP(i, 2*n){
    if(c[i].second == 0){
      if(ele >= 1){
        (ans *= ele) %= mod;
        ele--;
      }
      else{
        com++;
      }
    }
    else{
      if(com >= 1){
        (ans *= com) %= mod;
        com--;
      }
      else{
        ele++;
      }
    }
  }
  cout << ans << endl;
  
  return 0;
}

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