Submission #1519558

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define FOR(i, j, k) for(int i=j; i<=k; i++)
#define FFOR(i, j, k) for(int i=j; i<k; i++)
#define DFOR(i, j, k) for(int i=j; i>=k; i--)
#define bug(x) cerr<<#x<<" = "<<x<<'\n'
#define pb push_back
#define mp make_pair
typedef long long ll;
typedef long double ld;
template <typename T> inline void read(T &x){
    char c;
    bool nega=0;
    while((!isdigit(c=getchar()))&&(c!='-'));
    if(c=='-'){
        nega=1;
        c=getchar();
    }
    x=c-48;
    while(isdigit(c=getchar())) x=x*10+c-48;
    if(nega) x=-x;
}
template <typename T> inline void writep(T x){
    if(x>9) writep(x/10);
    putchar(x%10+48);
}
template <typename T> inline void write(T x){
    if(x<0){
        putchar('-');
        x=-x;
    }
    writep(x);
}
template <typename T> inline void writeln(T x){
    write(x);
    putchar('\n');
}
#define taskname "C"
int n;
int a;
int cnt[100001];
int main(){
    #ifdef Megumin
        if(fopen(taskname".inp", "r"))
            freopen(taskname".inp", "r", stdin);
    #endif // Megumin
    read(n);
    FOR(i, 1, n){
        read(a);
        cnt[a]++;
    }
    if(n%2) cnt[0]++;
    for(int i=n-1; i>=0; i-=2) if(cnt[i]!=2){
        puts("0");
        return 0;
    }
    int ans=1;
    DFOR(i, n/2, 1) ans=(ans*2)%1000000007;
    writeln(ans);
}

Submission Info

Judge Result