Submission #3604618

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Source Code Expand

#include <bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<(b);++i)
#define erep(i,a,b) for(int i=a;i<=(int)(b);++i)
#define per(i,a,b) for(int i=(a);i>(b);--i)
#define eper(i,a,b) for(int i=(a);i>=b;--i)
#define fore(x, a) for(auto &x : a)
#define pb push_back
#define mp make_pair
#define INF 100100100100
#define inf 2001001001
#define MOD 1000000007
#define ALL(x) begin(x),end(x)
using namespace std;
using ll = long long;
using pii = pair<int,int>;
using vii = vector<int>;
using vll = vector<ll>;
template<class T>using vv = vector<T>;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
template<class T>void show(const vector<T> &a) { for (int i = 0; i < (int)a.size(); ++i) cout << a[i] << (i != (int)a.size()-1 ? " " : "\n"); }
template<class T>T gcd(T a, T b){ return b ? gcd(b, a % b) : a; }
template<class T>T lcm(T a, T b){ return a / gcd(a, b) * b; }
int dy[]={0, 1, -1, 0};
int dx[]={1, 0, 0, -1};

ll mod_pow(ll x, ll y) {
  ll res = 1LL;
  while (y > 0) {
    if ((y & 1)) {
      res = res * x % MOD;
    }
    x = x * x % MOD;
    y >>= 1;
  }
  return res;
}

ll n, ans;
vll a;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
    cin >> n;
    a.resize(n);
    rep(i, 0, n) cin >> a[i];
    sort(ALL(a));
    rep(i, n % 2, n) {
      if (a[i] != a[i+1]) {
        cout << 0 << endl;
        return 0;
      }
      i++;
    }
    if (n % 2) ans = mod_pow(2, (n-1)/2);
    else ans = mod_pow(2, n/2);
    cout << ans << endl;
    return 0;
}

Submission Info

Judge Result