Submission #3419357

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Source Code Expand

#include<iostream>
#include<vector>
#include<queue>
#include<stack>
#include<string>
#include<cmath>
#include<algorithm>
#include<bitset>
#include<map>
#include<functional>
#include<set>
#include<numeric>

#pragma region
using namespace std;
#define FOR(i,r,n) for(ll i = (ll)(r); i < (ll)(n); i++)
#define rep(i,n) FOR(i,0LL,n)
#define RFOR(i,r,n) for(ll i=(ll)(n-1);i>=r;i--)
#define rrep(i,n) RFOR(i,0LL,n)
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define COUNT(a,y,x) upper_bound(all(a), y) - lower_bound(all(a), x)
#define UNIQUE(a) sort(all(a)); a.erase(unique(all(a)), a.end())
#define SUM(a) accumulate(all(a),0LL)
#define pb push_back
#define endl '\n'
typedef long long int ll;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef vector<string> vs;
typedef map<ll, ll> MAP;
const ll inf = 2222222222222222222LL;
const ll mod = 1000000007LL;

ll n = 0, m = 0, ans = 0, cnt = 0, tmp = 0, ma = -inf, mi = inf;
string s;
bool ok = true, flag = false;
ll dx[5] = { 1,-1,0,0,0 }, dy[5] = { 0,0,1,-1,0 };
ll ddx[9] = { 1,-1,0,0,1,1,-1,-1,0 }, ddy[9] = { 0,0,1,-1,1,-1,1,-1,0 };
#pragma endregion
#define MAX 222222


vll fac, inv, invfac;
void comb_set(ll x = MAX) {
  fac.resize(x + 1, 0);
  invfac.resize(x + 1, 0);
  inv.resize(x + 1, 0);
  fac[0] = inv[1] = invfac[0] = 1;
  FOR(i, 1, x + 1) (fac[i] = fac[i - 1] * i) %= mod;
  FOR(i, 2, x + 1) (inv[i] = (mod - mod / i) * inv[mod%i]) %= mod;
  FOR(i, 1, x + 1) (invfac[i] = invfac[i - 1] * inv[i]) %= mod;
}
ll comb(ll x, ll y) {
  if (x < y) return 1;
  return fac[x] * invfac[x - y] % mod * invfac[y] % mod;
}

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


  cin >> n;
  vpll v;
  pll p;
  comb_set();
  rep(i, n) {
	cin >> p.first;
	p.second = 0;
	v.pb(p);
  }
  rep(i, n) {
	cin >> p.first;
	p.second = 1;
	v.pb(p);
  }
  sort(all(v));
  ans = 1;
  ll acnt = 0, bcnt = 0;
  if (v[0].second) bcnt++;
  else acnt++;
  FOR(i, 1, 2 * n) {
	if (v[i].second != v[i - 1].second) {
	  if (v[i].second == 0) {
		if (bcnt >= acnt) {
		  (ans *= fac[acnt]) %= mod;
		  bcnt -= acnt;
		  acnt = 0;
		}
		else {
		  (ans *= comb(max(acnt, bcnt), min(acnt, bcnt))) %= mod;
		  m = min(acnt, bcnt);
		  (ans *= fac[m]) %= mod;
		  acnt -= m;
		  bcnt -= m;
		}
	  }
	  else {
		if (acnt >= bcnt) {
		  (ans *= fac[bcnt]) %= mod;
		  acnt -= bcnt;
		  bcnt = 0;
		}
		else {
		  (ans *= comb(max(acnt, bcnt), min(acnt, bcnt))) %= mod;
		  m = min(acnt, bcnt);
		  (ans *= fac[m]) %= mod;
		  acnt -= m;
		  bcnt -= m;
		}
	  }
	}
	if (v[i].second == 0) acnt++;
	else bcnt++;
	//cout << acnt << " " << bcnt << " " << ans << endl;
  }
  (ans *= fac[acnt]) %= mod;
  cout << ans << endl;

  return 0;
}

Submission Info

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