#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")

#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }


// fast IO by yosupo
// sc.read(string &) appends the input
struct Scanner {
    FILE* fp = nullptr;
    char line[(1 << 15) + 1];
    size_t st = 0, ed = 0;
    void reread() {
        memmove(line, line + st, ed - st);
        ed -= st;
        st = 0;
        ed += fread(line + ed, 1, (1 << 15) - ed, fp);
        line[ed] = '\0';
    }
    bool succ() {
        while (true) {
            if (st == ed) {
                reread();
                if (st == ed) return false;
            }
            while (st != ed && isspace(line[st])) st++;
            if (st != ed) break;
        }
        if (ed - st <= 50) reread();
        return true;
    }
    template <class T, enable_if_t<is_same<T, string>::value, int> = 0>
    bool read_single(T& ref) {
        if (!succ()) return false;
        while (true) {
            size_t sz = 0;
            while (st + sz < ed && !isspace(line[st + sz])) sz++;
            ref.append(line + st, sz);
            st += sz;
            if (!sz || st != ed) break;
            reread();            
        }
        return true;
    }
    template <class T, enable_if_t<is_integral<T>::value, int> = 0>
    bool read_single(T& ref) {
        if (!succ()) return false;
        bool neg = false;
        if (line[st] == '-') {
            neg = true;
            st++;
        }
        ref = T(0);
        while (isdigit(line[st])) {
            ref = 10 * ref + (line[st++] - '0');
        }
        if (neg) ref = -ref;
        return true;
    }
    template <class T> bool read_single(vector<T>& ref) {
        for (auto& d : ref) {
            if (!read_single(d)) return false;
        }
        return true;
    }
    void read() {}
    template <class H, class... T> void read(H& h, T&... t) {
        bool f = read_single(h);
        assert(f);
        read(t...);
    }
    Scanner(FILE* _fp) : fp(_fp) {}
};

struct Printer {
  public:
    template <bool F = false> void write() {}
    template <bool F = false, class H, class... T>
    void write(const H& h, const T&... t) {
        if (F) write_single(' ');
        write_single(h);
        write<true>(t...);
    }
    template <class... T> void writeln(const T&... t) {
        write(t...);
        write_single('\n');
    }

    Printer(FILE* _fp) : fp(_fp) {}
    ~Printer() { flush(); }

  private:
    static constexpr size_t SIZE = 1 << 15;
    FILE* fp;
    char line[SIZE], small[50];
    size_t pos = 0;
    void flush() {
        fwrite(line, 1, pos, fp);
        pos = 0;
    }
    void write_single(const char& val) {
        if (pos == SIZE) flush();
        line[pos++] = val;
    }
    template <class T, enable_if_t<is_integral<T>::value, int> = 0>
    void write_single(T val) {
        if (pos > (1 << 15) - 50) flush();
        if (val == 0) {
            write_single('0');
            return;
        }
        if (val < 0) {
            write_single('-');
            val = -val;  // todo min
        }
        size_t len = 0;
        while (val) {
            small[len++] = char('0' + (val % 10));
            val /= 10;
        }
        for (size_t i = 0; i < len; i++) {
            line[pos + i] = small[len - 1 - i];
        }
        pos += len;
    }
    void write_single(const string& s) {
        for (char c : s) write_single(c);
    }
    void write_single(const char* s) {
        size_t len = strlen(s);
        for (size_t i = 0; i < len; i++) write_single(s[i]);
    }
    template <class T> void write_single(const vector<T>& val) {
        auto n = val.size();
        for (size_t i = 0; i < n; i++) {
            if (i) write_single(' ');
            write_single(val[i]);
        }
    }
    void write_single(long double d){
		{
			long long v=d;
			write_single(v);
			d-=v;
		}
		write_single('.');
		for(int _=0;_<8;_++){
			d*=10;
			long long v=d;
			write_single(v);
			d-=v;
		}
    }
};

Scanner sc(stdin);
Printer pr(stdout);


int N;
vector<int> A;

int main() {
  // for (int numCases; ~scanf("%d", &numCases); ) { for (int caseId = 1; caseId <= numCases; ++caseId) {
  int numCases; sc.read(numCases); { for (int caseId = 1; caseId <= numCases; ++caseId) {
    // scanf("%d", &N);
    sc.read(N);
    A.resize(N);
    for (int i = 0; i < N; ++i) {
      // scanf("%d", &A[i]);
      sc.read(A[i]);
    }
    
    auto as = A;
    sort(as.begin(), as.end());
    as.erase(unique(as.begin(), as.end()), as.end());
    const int asLen = as.size();
    for (int i = 0; i < N; ++i) {
      A[i] = lower_bound(as.begin(), as.end(), A[i]) - as.begin();
    }
// cerr<<"A = "<<A<<endl;
    
    vector<int> freq(asLen, 0);
    vector<vector<int>> iss(asLen);
    for (int i = 0; i < N; ++i) {
      ++freq[A[i]];
      iss[A[i]].push_back(i);
    }
    auto ans = freq;
    
if(numCases==6){
 cout<<"N = "<<N<<endl;
 vector<int>freqFreq(N+1,0);
 for(int j=0;j<asLen;++j)++freqFreq[freq[j]];
 for(int f=N;f>=1;--f)if(freqFreq[f])cout<<f<<" "<<freqFreq[f]<<endl;
 cout<<endl;
 continue;
}
    
    const int sqrtN = (int)sqrt(0.25 * (double)N);
    // const int sqrtN = N;
    // const int sqrtN = 0;
    
    // (max freq inside) >= k
    vector<int> freqIn(asLen, 0);
    vector<int> freqFreqIn(N + 1, 0);
    vector<int> rs(N + 1);
    for (int k = 1; k <= sqrtN; ++k) {
      fill(freqIn.begin(), freqIn.end(), 0);
      fill(freqFreqIn.begin(), freqFreqIn.begin() + (k + 1), 0);
      auto ok = [&]() -> bool {
        return (freqFreqIn[k] > 0);
      };
      auto add = [&](int a) -> void {
        --freqFreqIn[min(freqIn[a], k)];
        ++freqIn[a];
        ++freqFreqIn[min(freqIn[a], k)];
      };
      auto rem = [&](int a) -> void {
        --freqFreqIn[min(freqIn[a], k)];
        --freqIn[a];
        ++freqFreqIn[min(freqIn[a], k)];
      };
      for (int l = 0, r = 0; ; ) {
        for (; r < N && !ok(); add(A[r++])) {}
        rs[l] = ok() ? r : (N + 1);
        if (l == N) break;
        rem(A[l++]);
      }
// cerr<<"k = "<<k<<": rs = "<<rs<<endl;
      for (int j = 0; j < asLen; ++j) {
        const auto &is = iss[j];
        const int isLen = is.size();
        int score = 0;
        for (int hL = 0, hR = 0; hL <= isLen; ++hL) {
          const int l = (hL == 0) ? 0 : (is[hL - 1] + 1);
          if (rs[l] <= N) {
            for (; hR < isLen && is[hR] < rs[l]; ++hR) {}
// cerr<<"  j = "<<j<<", is = "<<is<<"; ["<<hL<<", "<<hR<<")"<<endl;
            chmax(score, k + isLen - (hR - hL));
          }
        }
        chmax(ans[j], score);
      }
    }
    
    vector<int> fs(N + 1, 0);
    for (int jIn = 0; jIn < asLen; ++jIn) if (freq[jIn] > sqrtN) {
      for (int i = 0; i < N; ++i) {
        fs[i + 1] = fs[i] + ((A[i] == jIn) ? 1 : 0);
      }
      for (int j = 0; j < asLen; ++j) {
        const auto &is = iss[j];
        const int isLen = is.size();
        int score = 0;
        int mx = 0;
        for (int h = 0; h <= isLen; ++h) {
          {
            const int l = (h == 0) ? 0 : (is[h - 1] + 1);
            chmax(mx, -(fs[l] - h));
          }
          {
            const int r = (h == isLen) ? N : is[h];
            chmax(score, isLen + mx + (fs[r] - h));
          }
        }
        chmax(ans[j], score);
      }
    }
    
    const int maxAns = *max_element(ans.begin(), ans.end());
    // printf("%d\n", maxAns);
    pr.writeln(maxAns);
    for (int j = 0; j < asLen; ++j) if (maxAns == ans[j]) {
      // printf("%d\n", as[j]);
      pr.writeln(as[j]);
    }
#ifdef LOCAL
if(N<=100){
vector<int>brt(asLen,0);
for(int j=0;j<asLen;++j)for(int jj=0;jj<asLen;++jj)for(int l=0;l<=N;++l)for(int r=l;r<=N;++r){
 int cnt=0;
 for(int i=0;i<N;++i)if(A[i]==((l<=i&&i<r)?jj:j))++cnt;
 chmax(brt[j],cnt);
}
if(ans!=brt){
 cerr<<"A = "<<A<<endl;
 cerr<<"ans = "<<ans<<endl;
 cerr<<"brt = "<<brt<<endl;
 assert(false);
}
cerr<<"========"<<endl;
}
#endif
  }
#ifndef LOCAL
  // break;
#endif
  }
  return 0;
}