Submission #3607117

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Source Code Expand

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

using namespace std;

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

Submission Info

Judge Result