why incorrect？1-6WA、7-10TLE

#include<bits/stdc++.h>
using namespace std;
const int MOD=50021;
int Hash[MOD];
int main()
{
    //闭散列法
    int t;cin>>t;while(t--)
    {
        memset(Hash,0,sizeof Hash);
        int n;cin>>n;while(n--)
        {
            int num;cin>>num;
            int ind=(num%MOD+MOD)%MOD;
            bool exist=false;
            while(Hash[ind])
            {
                if(Hash[ind]==num)
                {exist=true;break;}
                ++ind;if(ind>=MOD)ind=0;
            }
            if(exist)continue;
            Hash[ind]=num;
            cout<<num<<' ';
        }
        cout<<endl;
    }
}