Submission #7014092

---

Source Code Expand

#include <bits/stdc++.h>
#define int long long
#define rep(a,b) for(int (a)=0; (a)<(int)(b); ++(a))
using namespace std;

constexpr int MOD=1000000007;

signed main(void){
  int N; cin>>N;
  map<int,int> A;
  rep(i,N){
    int ta; cin>>ta;
    ++A[ta];
  }
  bool able=true;
  int ans=0;
  if(N%2){
    able&=A[0]==1;
    for(int i=2;i<N;i+=2){
      able&=A[i]==2;
    }
    if(able){
      ans=1;
      rep(i,N/2){
        ans=ans*2%MOD;
      }
    }
  }
  else{
    for(int i=1;i<N;i+=2){
      able&=A[i]==2;
    }
    if(able){
      ans=1;
      rep(i,N/2){
        ans=ans*2%MOD;
      }
    }
  }
  cout<<ans;
}

Submission Info

Judge Result