Submission #1131177

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define sz(x) ((int) (x).size())
#define forn(i,n) for (int i = 0; i < int(n); ++i)
typedef long long ll;
typedef long long i64;
typedef long double ld;
const int inf = int(1e9) + int(1e5);
const ll infl = ll(2e18) + ll(1e10);

const int maxn = 100100;
int x[maxn];

const int mod = 1e9 + 7;
int mul(ll a, ll b) {
    return a * b % mod;
}

int main() {
    #ifdef LOCAL
    assert(freopen("a.in", "r", stdin));
    #else
    #endif
    int n;
    cin >> n;
    forn (i, n)
        cin >> x[i];
    sort(x, x + n);

    int res = 1;
    int rem = 0;
    forn (i, n) {
        int r = x[i];
        int k = i + 1 - rem;
        if (k > (r + 1) / 2) {
            res = mul(res, k);
            ++rem;
        }
    }
    for (int i = 1; i <= n - rem; ++i)
        res = mul(res, i);
    cout << res << '\n';
}

Submission Info

Judge Result