#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> a(n);
        for(int i = 0; i < n; ++i) cin >> a[i];

        string answer;
        for(int i = 0; i < n; ++i) answer += 'R';

        if(a[0] == a[n - 1]){
            cout << "NO" << '\n';
            continue;
        }
        cout << "YES\n";
        bool f = 0;
        for(int i = 0; i < n; ++i){
            if(a[0] != a[i] && a[n - 1] != a[i]){
                answer[i] == 'B';
                f = true;
                break;
            }
        }
        if(f == false) answer[1] == 'B';
        cout << answer << '\n';
    }
}