//Utkarsh.25dec
#include <bits/stdc++.h>
#define ll long long int
#define pb push_back
#define mp make_pair
#define mod 1000000007
#define vl vector <ll>
#define all(c) (c).begin(),(c).end()
using namespace std;
ll power(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll modInverse(ll a){return power(a,mod-2);}
const int N=500023;
bool vis[N];
vector <int> adj[N];
long long readInt(long long l,long long r,char endd){
    long long x=0;
    int cnt=0;
    int fi=-1;
    bool is_neg=false;
    while(true){
        char g=getchar();
        if(g=='-'){
            assert(fi==-1);
            is_neg=true;
            continue;
        }
        if('0'<=g && g<='9'){
            x*=10;
            x+=g-'0';
            if(cnt==0){
                fi=g-'0';
            }
            cnt++;
            assert(fi!=0 || cnt==1);
            assert(fi!=0 || is_neg==false);

            assert(!(cnt>19 || ( cnt==19 && fi>1) ));
        } else if(g==endd){
            if(is_neg){
                x= -x;
            }

            if(!(l <= x && x <= r))
            {
                cerr << l << ' ' << r << ' ' << x << '\n';
                assert(1 == 0);
            }

            return x;
        } else {
            assert(false);
        }
    }
}
string readString(int l,int r,char endd){
    string ret="";
    int cnt=0;
    while(true){
        char g=getchar();
        assert(g!=-1);
        if(g==endd){
            break;
        }
        cnt++;
        ret+=g;
    }
    assert(l<=cnt && cnt<=r);
    return ret;
}
long long readIntSp(long long l,long long r){
    return readInt(l,r,' ');
}
long long readIntLn(long long l,long long r){
    return readInt(l,r,'\n');
}
string readStringLn(int l,int r){
    return readString(l,r,'\n');
}
string readStringSp(int l,int r){
    return readString(l,r,' ');
}
void solve()
{
    int n=readInt(1,100000,'\n');
    string s=readString(n,n,'\n');
    int freq[30]={0};
    for(auto ch:s)
    {
        assert(ch>='a' && ch<='z');
        freq[ch-'a']++;
    }
    char ans[n+1];
    set <int> c1,c2,c3;
    for(int i=1;i<=n;i++)
    {
        if(i%3==1)
            c1.insert(i);
        if(i%3==2)
            c2.insert(i);
        if(i%3==0)
            c3.insert(i);
    }
    vector <pair<int,char>> v;
    for(char ch='a';ch<='z';ch++)
        v.pb(mp(freq[ch-'a'],ch));
    sort(all(v));
    reverse(all(v));
    int limit=(n+2)/3;
    int bad=0;
    for(char ch='a';ch<='z';ch++)
    {
        if(freq[ch-'a']>limit)
        {
            cout<<"NO\n";
            return;
        }
        if(freq[ch-'a']==limit)
            bad++;
    }
    int afford=n%3;
    if(afford==0)
        afford=3;
    if(bad>afford)
    {
        cout<<"NO\n";
        return;
    }
    cout<<"YES\n";
    for(auto it:v)
    {
        // cout<<it.first<<' '<<it.second<<'\n';
        if(it.first==limit)
        {
            if(c1.size()==limit)
            {
                while(c1.size()>0)
                {
                    auto it2=c1.begin();
                    ans[(*it2)]=it.second;
                    c1.erase(it2);
                }
                continue;
            }
            if(c2.size()==limit)
            {
                while(c2.size()>0)
                {
               
                    auto it2=c2.begin();
                    ans[(*it2)]=it.second;
                    c2.erase(it2);
                }
                continue;
            }
            if(c3.size()==limit)
            {
                while(c3.size()>0)
                {
                    auto it2=c3.begin();
                    ans[(*it2)]=it.second;
                    c3.erase(it2);
                }
                continue;
            }
        }
        else
        {
            for(int i=1;i<=it.first;i++)
            {
                if(c3.size()>0)
                {
                    auto it2=c3.begin();
                    ans[(*it2)]=it.second;
                    c3.erase(it2);
                    continue;
                }
                if(c2.size()>0)
                {
                    auto it2=c2.begin();
                    ans[(*it2)]=it.second;
                    c2.erase(it2);
                    continue;
                }
                if(c1.size()>0)
                {
                    auto it2=c1.begin();
                    ans[(*it2)]=it.second;
                    c1.erase(it2);
                    continue;
                }
            }
        }
    }
    for(int i=1;i<=n;i++)
        cout<<ans[i];
    cout<<'\n';
}
int main()
{
    #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    #endif
    ios_base::sync_with_stdio(false);
    cin.tie(NULL),cout.tie(NULL);
    int T=readInt(1,100000,'\n');
    while(T--)
        solve();
    assert(getchar()==-1);
    cerr << "Time : " << 1000 * ((double)clock()) / (double)CLOCKS_PER_SEC << "ms\n";
}