Submission #3607127

---

Source Code Expand

#include <iostream>
#include <vector>
#include <algorithm>

#define MOD 1000000007

typedef long long ll;

using namespace std;

int main() {
    ll n, ans = 1;
    cin >> n;
    vector<ll> a(n);
    for (ll i = 0; i < n; ++i) cin >> a.at(i);
    sort(a.begin(), a.end());
    for (ll i = n - 1; i >= 0; --i) {
        if (a.at(i) != (i + n % 2) / 2 * 2 + (n - 1) % 2) {
            cout << 0 << endl;
            return 0;
        }
    }
    for (ll i = 0; i < n / 2; ++i) ans = ans * 2 % MOD;
    cout << ans << endl;
    return 0;
}

Submission Info

Judge Result