#include <bits/stdc++.h>

#define int long long

using namespace std;

signed main() {
    int t;
    cin >> t;
    while(t--){
        int n;
        cin >> n;
        vector<int> v(n);
        for(int i = 0; i < n; ++i){
            cin >> v[i];
        }

        string ans;
        ans.resize(n);

        if(v[0] == v.back()){
            cout << "NO\n";
        }else{
            bool q = false;

            for(int i = 0; i < n; i++){
                if(v[i] != v[0] && v[i] != v.back() && !q){
                    q = true;
                    ans[i] = 'B';
                }else{
                    ans[i] = 'R';
                }
            }

            if(!q){
                ans[1] = 'B';
            }
            cout << "YES" << '\n' << ans << '\n';
        }


    }
}