#include "bits/stdc++.h"
#define rep(i, a, n) for (auto i = a; i <= (n); ++i)
#define revrep(i, a, n) for (auto i = n; i >= (a); --i)
#define all(a) a.begin(), a.end()
#define sz(a) (int)(a).size()
template<class T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T &a, T b) { if (b < a) { a = b; return 1; } return 0; }
using namespace std;

template<class A, class B> string to_string(const pair<A, B> &p);
string to_string(const string &s) { return '"' + s + '"'; }
string to_string(const char *s) { return to_string((string) s); }
string to_string(char c) { return "'" + string(1, c) + "'"; }
string to_string(bool x) { return x ? "true" : "false"; }
template<class A> string to_string(const A &v) {
	bool first = 1;
	string res = "{";
	for (const auto &x: v) {
		if (!first) res += ", ";
		first = 0;
		res += to_string(x);
	}
	res += "}";
	return res;
}
template<class A, class B> string to_string(const pair<A, B> &p) {
	return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

void debug_out() { cerr << endl; }
template<class H, class... T> void debug_out(const H& h, const T&... t) {
	cerr << " " << to_string(h);
	debug_out(t...);
}
#ifndef ONLINE_JUDGE
	#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
	#define debug(...) if(0) puts("No effect.")
#endif

using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vvi = vector<vi>;


int main() {
	ios::sync_with_stdio(0); cin.tie(0);
	
	int cas; cin >> cas; while (cas--) {
		int n; cin >> n;
		vi as(n);
		for (auto &x: as) cin >> x;
		vi nums = as;
		sort(all(nums)); nums.erase(unique(all(nums)), nums.end());
		for (auto &x: as) x = lower_bound(all(nums), x) - nums.begin();
		int tot = sz(nums);
		vi cnt(tot);
		for (auto x: as) cnt[x]++;
		vi ans = cnt;
		
		int thr = sqrt(n) + 0.5;
		rep(occ, 1, thr) {
			vi ocnt = cnt, icnt(tot);
			vi times(n + 1);
			times[0] = tot;
			int mx = 0;
			auto add = [&](int x) {
				times[icnt[x]]--;
				icnt[x]++;
				ocnt[x]--;
				times[icnt[x]]++;
				chmax(mx, icnt[x]);
			};
			auto remove = [&](int x) {
				times[icnt[x]]--;
				icnt[x]--;
				ocnt[x]++;
				times[icnt[x]]++;
				if (times[mx] == 0) mx--;
			};
			int ptr = 0;
			auto seq_add = [&]() {
				while (ptr < n && mx != occ) {
					add(as[ptr]);
					ptr++;
				}
			};
			seq_add();
			if (mx != occ) continue;
			rep(i, 0, tot - 1) chmax(ans[i], ocnt[i] + occ);
			rep(i, 0, n - 1) {
				int x = as[i];
				remove(x);
				seq_add();
				if (mx != occ) break;
				chmax(ans[x], ocnt[x] + occ);
			}
		}

		vvi pls(tot);
		rep(i, 0, n - 1) {
			int x = as[i];
			pls[x].push_back(i);
		}

		rep(x, 0, tot - 1) if (sz(pls[x]) > thr) {
			vi pres(n + 1);
			for (auto p: pls[x]) pres[p + 1] = 1;
			rep(i, 0, sz(pres) - 2) pres[i + 1] += pres[i];
			rep(y, 0, tot - 1) if (y != x) {
				int mnpre = 0;
				int mx = 0;
				rep(ind, 0, sz(pls[y]) - 1) {
					int p = pls[y][ind];
					int cur = pres[p] - ind;
					chmax(mx, cur - mnpre + sz(pls[y]));
					chmin(mnpre, pres[p + 1] - (ind + 1));
				}
				chmax(ans[y], mx);
			}
		}

		int maxans = *max_element(all(ans));
		printf("%d\n", maxans);
		rep(i, 0, sz(ans) - 1) {
			int val = nums[i];
			if (ans[i] == maxans) printf("%d\n", val);
		}
	}
	return 0;
}