Submission #4923701

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Source Code Expand

#include <bits/stdc++.h>

#define CEIL(a,b) ((a) / (b) + ((a) % (b) == 0 ? 0 : 1))

using namespace std;
using ll = long long;
using pii = pair<int, int>;

constexpr int MOD = int(1e9 + 7);
constexpr int INF = int(1e9 + 1);
constexpr ll LLINF = ll(4 * 1e18 + 1);
// constexpr int INF = 2147483647; // 2 * 1e9
// constexpr ll LLINF = 9223372036854775807; // 9 * 1e18

const int dx[] = {1, 0, -1, 0, 1, -1, -1, 1, 0};
const int dy[] = {0, 1, 0, -1, 1, 1, -1, -1, 0};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(10);
    int n;
    cin >> n;
    vector<pii> a;
    for(int i = 0; i < n; ++i){
        int t;
        cin >> t;
        a.push_back({t, 0});
    }
    for(int i = 0; i < n; ++i){
        int t;
        cin >> t;
        a.push_back({t, 1});
    }
    sort(begin(a), end(a));

    int cnt_pc = 0, cnt_power = 0;
    ll ans = 1;
    for(int i = 0; i < 2 * n; ++i){
        if(a[i].second == 0){
            if(cnt_power == 0){
                ++cnt_pc;
            }
            else{
                ans *= cnt_power;
                ans %= MOD;
                --cnt_power;
            }
        }
        if(a[i].second == 1){
            if(cnt_pc == 0){
                ++cnt_power;
            }
            else{
                ans *= cnt_pc;
                ans %= MOD;
                --cnt_pc;
            }
        }
    }
    
    cout << ans << "\n";
    
    return 0;
}

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