Even Subset Sum Problem CodeForces - 1323A 水dp

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
const int N=1010;
int a[N];
int sum;
int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        int n;
        cin>>n;
        sum=0;
        int pos=0;
        for(int i=1;i<=n;i++)
        {
            cin>>a[i];
            sum+=a[i];
            if(a[i]%2)
                pos=i;
        }
        if(sum%2==0)
        {
            cout<<n<<endl;
            for(int i=1;i<=n;i++)
                cout<<i<<" ";
            cout<<endl; 
        }
        else if(sum%2==1)
        {
            if(n==1)
                cout<<"-1"<<endl;
            else
            {
                cout<<n-1<<endl; 
                for(int i=1;i<=n;i++)
                {
                    if(i==pos)
                        continue;
                    else
                        cout<<i<<" ";
                }
                cout<<endl;
            }
        }
    }
}