Submission #6979732

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Source Code Expand

#include <bits/stdc++.h>
typedef long long ll;
typedef long double ld;
const int INF=1e9,MOD=1e9+7,ohara=1e6+10;
const ll LINF=1e18;
using namespace std;

#define rep(i,n) for(int (i)=0;(i)<(int)(n);(i)++)
#define rrep(i,a,b) for(int i=(a);i<(b);i++)
#define rrrep(i,a,b) for(int i=(a);i>=(b);i--)
#define all(v) (v).begin(), (v).end()
#define Size(n) (n).size()
#define Cout(x) cout<<(x)<<endl
#define doublecout(a) cout<<fixed<<setprecision(15)<<a<<endl;
#define Cerr(x) cerr<<(x)<<endl
#define fi first
#define se second
#define P pair<ll,ll> 
#define m_p make_pair
#define V vector<ll> 
#define U_MAP unordered_map<ll,ll>

ll n,cnt,ans,a[ohara],b,c,d,tmp,tmpp,m,h,w,x,y,sum,pos,k;
ld doua;
int dy[]={1,0,-1,0};
int dx[]={0,1,0,-1};
//int dy[]={-1,0,1,-1,1,-1,0,1};
//int dx[]={-1,-1,-1,0,0,1,1,1};
string alph("abcdefghijklmnopqrstuvwxyz"),s;
bool fl;
struct edge{int to,cost;};

//-------------------------↓↓↓↓↓↓------------------------

//------ 自分を天才だと信じる ------

int main(void){
        cin.tie(0);
        cout.tie(0);
    ios::sync_with_stdio(false);

    cin>>n;
    rep(i,n)cin>>a[i];
    sort(a,a+n);
    if(n%2==1){
        if(a[0]!=0){
            Cout(0);
            return 0;
        }
        ll want=2;
        rrep(i,1,n){
            if(a[i]!=want){
                Cout(0);
                return 0;
            }
            i++;
            if(a[i]!=want){
                Cout(0);
                return 0;
            }
            want+=2;
        }
    }
    else{
        ll want=1;
        rep(i,n){
            if(a[i]!=want){
                Cout(0);
                return 0;
            }
            i++;
            if(a[i]!=want){
                Cout(0);
                return 0;
            }
            want+=2;
        }
    }
    n/=2;
    ans=1;
    rep(i,n){
        ans*=2;
        ans%=MOD;
    }
    Cout(ans);
    return 0;
}

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