Submission #1520124

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Source Code Expand

# include <iostream>
# include <algorithm>
# include <vector>
# include <string>
# include <set>
# include <map>
# include <cmath>
# include <iomanip>
# include <functional>
# include <utility>
# include <stack>
# include <queue>
# include <list>
# include <unordered_map>
constexpr int MOD = 1000000000 + 7;
constexpr int INF = 2000000000;
using namespace std;
using LL = long long;

int C[100001];

int main() {
	int n;
	cin >> n;
	int a;
	for (int i = 0; i < n; i++) {
		cin >> a;
		C[a]++;
	}
	LL ans = 1;
	if (n % 2 == 0) {
		bool isok = true;
		for (int i = 1; i < n; i += 2) {
			if (C[i] != 2)isok = false;
		}
		if (isok) {
			for (int i = 0; i < n / 2; i++) {
				ans = ans * 2 % MOD;
			}
			cout << ans << endl;
		}
		else {
			cout << 0 << endl;
		}
	}
	else {
		bool isok = true;
		if (C[0] != 1)isok = false;
		for (int i = 2; i < n; i += 2) {
			if (C[i] != 2)isok = false;
		}
		if (isok) {
			for (int i = 0; i < n / 2; i++) {
				ans = ans * 2 % MOD;
			}
			cout << ans << endl;
		}
		else {
			cout << 0 << endl;
		}
	}
}

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