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#pragma GCC optimize("O2,no-stack-protector,unroll-loops")
#define ll long long
#define pb push_back
#define ipar(arr, n) vector<ll> arr(n); for(int i=0;i<n;i++) cin>>arr[i];
#include <cmath>
#include <bits/stdc++.h>
#define pii pair<int, int>;
#define pll pair<ll, ll>;
using namespace std;
 
 
void solve(){
    ll n;cin>>n;
    ipar(arr,n);
    vector<int>freq(26,0);
    string s;
    for(int a=0;a<n;a++){
        for(int i=0;i<26;i++){
            if(freq[i]!=arr[a]) continue;
            freq[i]++;
            s+=char('a'+i);
            break;
        }
    }
    cout<<s<<"\n";
}
 
 
signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    int t;
	cin>>t;
	while(t--) solve();
}