B. Mocha and Red and Blue（贪心）-蒲公英云

B. Mocha and Red and Blue（贪心）

（1）如果第一个位置是问号，分别把当做是R/B，往下模拟
（2）如果第一个位置是B，那就直接往下模拟
（3）如果第一个位置是R，还是直接往下模拟
第二个和第三个只需要一个字符串组就可以完成，但为了copy代码，以及适应下面的求和取最小的计算，需要变成两个字符串组。

// Problem: B. Mocha and Red and Blue
// Contest: Codeforces - Codeforces Round #738 (Div. 2)
// URL: https://codeforces.com/contest/1559/problem/B
// Memory Limit: 256 MB
// Time Limit: 1000 ms
// 
// Powered by CP Editor (https://cpeditor.org)
#include<iostream>
#include<cstdio>
#include<string>
#include<ctime>
#include<cmath>
#include<cstring>
#include<algorithm>
#include<stack>
#include<climits>
#include<queue>
#include<map>
#include<set>
#include<sstream>
#include<cassert>
#include<bitset>
#include<list>
#include<unordered_map>
using namespace std;
#define lowbit(x) (x&-x)
#define pf(a) printf("%d\n",a)
#define mem(x,y) memset(x,y,sizeof(x))
#define dbg(x) cout << #x << " = " << x << endl
#define rep(i,l,r) for(int i = l; i <= r; i++)
#define fep(i,a,b) for(int i=b;i>=a;--i)
typedef long long ll;
typedef unsigned long long ull;
const int inf=0x3f3f3f3f;
const int N=1e2+100;
int n;
char a[N],b[N],c[N];
void solve()
{ 
    cin >> n;
    rep(i,1,n) cin >> a[i];
    if(a[1]=='?')
    { 
        b[1] = 'B';
        c[1] = 'R';
        rep(i,2,n)
        { 
            if(a[i]!='?') 
            { 
                b[i] = a[i];
                c[i] = a[i];
                continue;
            }
            if(b[i-1]=='B') b[i]='R';
            if(b[i-1]=='R') b[i]='B';
            if(c[i-1]=='B') c[i]='R';
            if(c[i-1]=='R') c[i]='B';
        }
    }
    else if(a[1]=='B')
    { 
        b[1] = 'B';
        c[1] = 'B';
        rep(i,2,n)
        { 
            if(a[i]!='?') 
            { 
                b[i] = a[i];
                c[i] = a[i];
                continue;
            }
            if(b[i-1]=='B') b[i]='R';
            if(b[i-1]=='R') b[i]='B';
            if(c[i-1]=='B') c[i]='R';
            if(c[i-1]=='R') c[i]='B';
        }
    }
    else{ 
        b[1] = 'R';
        c[1] = 'R';
        rep(i,2,n)
        { 
            if(a[i]!='?') 
            { 
                b[i] = a[i];
                c[i] = a[i];
                continue;
            }
            if(b[i-1]=='B') b[i]='R';
            if(b[i-1]=='R') b[i]='B';
            if(c[i-1]=='B') c[i]='R';
            if(c[i-1]=='R') c[i]='B';
        }
    }
    int a1=0, a2=0;
    rep(i,1,n-1)
    { 
        if(b[i]==b[i+1]) a1++;
        if(c[i]==c[i+1]) a2++;
    }
    if(a1>=a2) rep(i,1,n) cout << c[i];
    else rep(i,1,n) cout << b[i];
    cout << endl; 
}
int main()
{ 
    ios::sync_with_stdio(false);cin.tie(0);
    int Case;cin >> Case;
    while(Case--)
        solve();
    return 0;
}