Submission #1349807

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Source Code Expand

// clang-format off
#include <bits/stdc++.h>
#define int long long
#define main signed main()
// #define main int main()
#define loop(i, a, n) for (int i = (a); i < (n); i++)
#define rep(i, n) loop(i, 0, n)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define prec(n) fixed << setprecision(n)
#define stlice(from, to) substr(from, (to) - (from) + 1)
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
using namespace std;
using pii = pair<int, int>;
using vi = vector<int>;
using vd = vector<double>;
using vc = vector<char>;
using vb = vector<bool>;
using vs = vector<string>;
using vpii = vector<pii>;
using vvi = vector<vi>;
using vvb = vector<vb>;
using vvpii = vector<vpii>;
template<typename A> using fn = function<A>;
constexpr int INF = sizeof(int) == sizeof(long long) ? 1000000000000000000LL : 1000000000;
constexpr int MOD = 1000000007;
constexpr double PI = acos(-1);
template<typename A, typename B> bool cmin(A &a, const B &b) { return a > b ? (a = b, true) : false; }
template<typename A, typename B> bool cmax(A &a, const B &b) { return a < b ? (a = b, true) : false; }
constexpr bool odd(const int &n) { return n & 1; }
constexpr bool even(const int &n) { return !odd(n); }
void solve();
main { solve(); return 0; }
// clang-format on

constexpr int powm(int a, int b, const int &m) {
  int c = 1;
  while (b) {
    if (odd(b)) c = (c * a) % m;
    b >>= 1;
    a = (a * a) % m;
  }
  return c;
}

void solve() {
  int n;
  cin >> n;
  vi t(n);
  rep(i, n) {
    int a;
    cin >> a;
    t[a]++;
  }
  if (any_of(all(t), [](int x) { return x > 2; }) || t[0] > 1) {
    cout << 0 << endl;
    return;
  }
  cout << powm(2, n / 2, MOD) << endl;
}

Submission Info

Judge Result