Submission #1070324

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Source Code Expand

#include <iostream>
#include <vector>
#include <cmath>

#define MOD 1000000007

using namespace std;

int main() {
    int n;
    int a[n];

    cin >> n;

    int num[n];
    for (int i = 0; i < n; i++) {
        num[i] = 0;
    }

    for (int i = 0; i < n; i++) {
        cin >> a[i];

        for (int j = 0; j <= n; j++) {
            if (j == a[i]) {
                num[j]++;
            }
        }
    }


    long long int ans = 0;
    bool is_correct = true;

    if (n % 2 == 1) {
        if (num[0] != 1) { is_correct = false; }

        for (int i = 2; i <= n - 1; i += 2) {
            if (num[i] != 2) {
                is_correct = false;
                break;
            }
        }
        if (is_correct) {
            int tmp = (n - 1) / 2;
            ans = 1;
            for (int i = 0; i < tmp; i++) {
                ans *= 2;
            }
        } else {
            ans = 0;
        }
    } else {
        if (num[0] != 0) { is_correct = false; }

        for (int i = 1; i <= n - 1; i += 2) {
            if (num[i] != 2) {
                is_correct = false;
                break;
            }
        }

        if (is_correct) {
            int tmp = n / 2;
            ans = 1;
            for (int i = 0; i < tmp; i++) {
                ans *= 2;
            }
        } else {
            ans = 0;
        }

    }

        ans = ans % MOD;

    cout << ans << endl;

    return 0;
}

Submission Info

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