Submission #1000705

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Source Code Expand

class in{struct It{int it;const bool rev;explicit constexpr It(int it_, bool rev=false):it(it_),rev(rev){}int operator*(){return it;}bool operator!=(It& r){return it!=r.it;}void operator++(){rev?--it:++it;}};const It i,n;public:explicit constexpr in(int n):i(0),n(n<0?0:n){}explicit constexpr in(int i,int n):i(i,n<i),n(n){}const It& begin(){return i;}const It& end(){return n;}};

#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
const i64 MOD = 1e9 + 7;
int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    vector<int> a(n), b(n), c(n + 1, -2);
    for(auto& x : a) cin >> x;
    for(auto& x : b) cin >> x;
    sort(a.begin(), a.end());
    sort(b.begin(), b.end());
    vector<i64> fact(n + 1, 0);
    fact[0] = fact[1] = 1LL;
    for(i64 i : in(2, n + 1))
      fact[i] = fact[i - 1] * i % MOD;
    i64 ans = 1LL;
    for(int _ : in(2)) {
        vector<bool> used(n, false);
        for(int i = 0; i < n; ++i) {
            if(used[i]) continue;
            auto it = upper_bound(a.begin(), a.end(), b[i]) - a.begin();
            int num = it - i;
            if(num < 0) continue;
            (ans *= fact[num]) %= MOD;
            for(int j : in(i, it)) used[j] = true;
        }
        swap(a, b);
    }
    cout << ans << endl;
    return 0;
}

Submission Info

Judge Result