Language: C++

#include <bits/stdc++.h>
// created [2019/11/23] 21:33:04
#pragma GCC diagnostic ignored "-Wsign-compare"
#pragma GCC diagnostic ignored "-Wsign-conversion"

using i32 = int32_t;
using i64 = int64_t;
using u32 = uint32_t;
using u64 = uint64_t;
using uint = unsigned int;
using usize = std::size_t;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
template<typename T> constexpr T popcount(const T u) { return u ? static_cast<T>(__builtin_popcountll(static_cast<u64>(u))) : static_cast<T>(0); }
template<typename T> constexpr T log2p1(const T u) { return u ? static_cast<T>(64 - __builtin_clzll(static_cast<u64>(u))) : static_cast<T>(0); }
template<typename T> constexpr T msbp1(const T u) { return log2p1(u); }
template<typename T> constexpr T lsbp1(const T u) { return __builtin_ffsll(u); }
template<typename T> constexpr T clog(const T u) { return u ? log2p1(u - 1) : static_cast<T>(u); }
template<typename T> constexpr bool ispow2(const T u) { return u and (static_cast<u64>(u) & static_cast<u64>(u - 1)) == 0; }
template<typename T> constexpr T ceil2(const T u) { return static_cast<T>(1) << clog(u); }
template<typename T> constexpr T floor2(const T u) { return u == 0 ? static_cast<T>(0) : static_cast<T>(1) << (log2p1(u) - 1); }
template<typename T> constexpr bool btest(const T mask, const usize ind) { return static_cast<bool>((static_cast<u64>(mask) >> ind) & static_cast<u64>(1)); }
template<typename T> void bset(T& mask, const usize ind) { mask |= (static_cast<T>(1) << ind); }
template<typename T> void breset(T& mask, const usize ind) { mask &= ~(static_cast<T>(1) << ind); }
template<typename T> void bflip(T& mask, const usize ind) { mask ^= (static_cast<T>(1) << ind); }
template<typename T> void bset(T& mask, const usize ind, const bool b) { (b ? bset(mask, ind) : breset(mask, ind)); }
template<typename T> constexpr T bcut(const T mask, const usize ind) { return ind == 0 ? static_cast<T>(0) : static_cast<T>((static_cast<u64>(mask) << (64 - ind)) >> (64 - ind)); }
template<typename T> bool chmin(T& a, const T& b) { return (a > b ? a = b, true : false); }
template<typename T> bool chmax(T& a, const T& b) { return (a < b ? a = b, true : false); }
constexpr unsigned int mod                  = 1000000007;
template<typename T> constexpr T inf_v      = std::numeric_limits<T>::max() / 4;
template<typename Real> constexpr Real pi_v = Real{3.141592653589793238462643383279502884};

template<typename T>
T read()
{
    T v;
    return std::cin >> v, v;
}
template<typename T, typename... Args>
auto read(const usize size, Args... args)
{
    std::vector<decltype(read<T>(args...))> ans(size);
    for (usize i = 0; i < size; i++) { ans[i] = read<T>(args...); }
    return ans;
}
template<typename... Types>
auto reads() { return std::tuple<std::decay_t<Types>...>{read<Types>()...}; }
#    define SHOW(...) static_cast<void>(0)

template<typename T>
std::vector<T> make_v(const usize size, const T v) { return std::vector<T>(size, v); }
template<typename... Args>
auto make_v(const usize size, Args... args) { return std::vector<decltype(make_v(args...))>(size, make_v(args...)); }
int main()
{
    const int N = read<int>();
        assert(A.size() == N);
        std::cout << "?";
        for (const int e : A) { std::cout << " " << e + 1; }
        std::cout << std::endl;
        const auto rep = read<std::string>();
        if (rep == "-1") { return -1; }
        return (rep == "Blue" ? 1 : 0);
    };
    auto answer = [&](const std::vector<int>& Ans) {
        assert(Ans.size() == 2 * N);
        std::cout << "! ";
        for (const int e : Ans) { std::cout << (e == 0 ? 'R' : 'B'); }
        std::cout << std::endl;
    };
    std::vector<int> ren(2 * N);
    std::vector<int> ans(2 * N, -1);
    std::deque<int> A;
    for (int i = 0; i < N; i++) {
        if (A.empty()) {
            for (int j = 0; j < N; j++) { A.push_back(j); }
        }
        ren[i] = ask(A);
        A.pop_front();
        A.push_back((i + N) % (2 * N));
    }

    int r = -1, b = -1;
    for (int i = 0; i < 2 * N; i++) {
        if (ren[i] != ren[i + 1]) {
            (ren[i] == 0 ? r : b) = i;
            (ren[i] == 0 ? b : r) = (i + N) % (2 * N);
            break;
        }
    }
    std::vector<int> L, R;
    for (int i = (r + 1) % (2 * N); i != b; (i += 1) %= (2 * N)) { L.push_back(i); }
    for (int i = (b + 1) % (2 * N); i != r; (i += 1) %= (2 * N)) { R.push_back(i); }
    SHOW(r, b);
    ans[r] = 0, ans[b] = 1;
    SHOW(L, R);
    for (const int e : L) {
        std::deque<int> a{r, b};
        for (const int e2 : L) {
            if (e2 == e) { continue; }
            a.push_back(e2);
        }
        const int blue = ask(a);
        ans[e]         = 1 - blue;
    }
    for (const int e : R) {
        std::deque<int> a{r, b};
        for (const int e2 : R) {
            if (e2 == e) { continue; }
            a.push_back(e2);
        }
        const int blue = ask(a);
        ans[e]         = 1 - blue;
    }
    SHOW(ans);
    answer(ans);
    return 0;
}


Compiler output:
In file included from /usr/include/c++/14/cassert:44,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:106,
                 from a.cc:1:
a.cc: In function 'int main()':
a.cc:59:16: error: 'A' was not declared in this scope
   59 |         assert(A.size() == N);
      |                ^
a.cc: At global scope:
a.cc:67:20: error: non-local lambda expression cannot have a capture-default
   67 |     auto answer = [&](const std::vector<int>& Ans) {
      |                    ^
a.cc: In lambda function:
a.cc:68:34: error: 'N' was not declared in this scope
   68 |         assert(Ans.size() == 2 * N);
      |                                  ^
a.cc: At global scope:
a.cc:73:30: error: 'N' was not declared in this scope
   73 |     std::vector<int> ren(2 * N);
      |                              ^
a.cc:74:30: error: 'N' was not declared in this scope
   74 |     std::vector<int> ans(2 * N, -1);
      |                              ^
a.cc:76:5: error: expected unqualified-id before 'for'
   76 |     for (int i = 0; i < N; i++) {
      |     ^~~
a.cc:76:21: error: 'i' does not name a type
   76 |     for (int i = 0; i < N; i++) {
      |                     ^
a.cc:76:28: error: 'i' does not name a type
   76 |     for (int i = 0; i < N; i++) {
      |                            ^
a.cc:86:5: error: expected unqualified-id before 'for'
   86 |     for (int i = 0; i < 2 * N; i++) {
      |     ^~~
a.cc:86:21: error: 'i' does not name a type
   86 |     for (int i = 0; i < 2 * N; i++) {
      |                     ^
a.cc:86:32: error: 'i' does not name a type
   86 |     for (int i = 0; i < 2 * N; i++) {
      |                                ^
a.cc:94:5: error: expected unqualified-id before 'for'
   94 |     for (int i = (r + 1) % (2 * N); i != b; (i += 1) %= (2 * N)) { L.push_back(i); }
      |     ^~~
a.cc:94:37: error: 'i' does not name a type
   94 |     for (int i = (r + 1) % (2 * N); i != b; (i += 1) %= (2 * N)) { L.push_back(i); }
      |                                     ^
a.cc:94:47: error: expected ')' before '+=' token
   94 |     for (int i = (r + 1) % (2 * N); i != b; (i += 1) %= (2 * N)) { L.push_back(i); }
      |                                             ~ ^~~
      |                                               )
a.cc:95:5: error: expected unqualified-id before 'for'
   95 |     for (int i = (b + 1) % (2 * N); i != r; (i += 1) %= (2 * N)) { R.push_back(i); }
      |     ^~~
a.cc:95:37: error: 'i' does not name a type
   95 |     for (int i = (b + 1) % (2 * N); i != r; (i += 1) %= (2 * N)) { R.push_back(i); }
      |                                     ^
a.cc:95:47: error: expected ')' before '+=' token
   95 |     for (int i = (b + 1) % (2 * N); i != r; (i += 1) %= (2 * N)) { R.push_back(i); }
      |                                             ~ ^~~
      |                                               )
a.cc:50:23: error: expected unqualified-id before 'static_cast'
   50 | #    define SHOW(...) static_cast<void>(0)
      |                       ^~~~~~~~~~~
a.cc:96:5: note: in expansion of macro 'SHOW'
   96 |     SHOW(r, b);
      |     ^~~~
a.cc:97:5: error: 'ans' does not name a type
   97 |     ans[r] = 0, ans[b] = 1;
      |     ^~~
a.cc:50:23: error: expected unqualified-id before 'static_cast'
   50 | #    define SHOW(...) static_cast<void>(0)
      |                       ^~~~~~~~~~~
a.cc:98:5: note: in expansion of macro 'SHOW'
   98 |     SHOW(L, R);
      |     ^~~~
a.cc:99:5: error: expected unqualified-id before 'for'
   99 |     for (const int e : L) {
      |     ^~~
a.cc:108:5: error: expected unqualified-id before 'for'
  108 |     for (const int e : R) {
      |     ^~~
a.cc:50:23: error: expected unqualified-id before 'static_cast'
   50 | #    define SHOW(...) static_cast<void>(0)
      |                       ^~~~~~~~~~~
a.cc:117:5: note: in expansion of macro 'SHOW'
  117 |     SHOW(ans);
      |     ^~~~
a.cc:118:11: error: expected constructor, destructor, or type conversion before '(' token
  118 |     answer(ans);
      |           ^
a.cc:119:5: error: expected unqualified-id before 'return'
  119 |     return 0;
      |     ^~~~~~
a.cc:120:1: error: expected declaration before '}' token
  120 | }
      | ^