B_Sequence_Game.cpp

#include <bits/stdc++.h>
using namespace std;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t;
    cin >> t;
    while (t--)
    {
        int n;
        cin >> n;
        vector<long long> b(n);
        for (int i = 0; i < n; i++)
            cin >> b[i];

        vector<long long> a;
        a.push_back(b[0]);
        for (int i = 1; i < n; i++)
        {
            if (b[i - 1] <= b[i])
            {
                a.push_back(b[i]);
            }
            else
            {
                a.push_back(b[i - 1]); // big one first
                a.push_back(b[i]);     // then the smaller one
            }
        }

        cout << a.size() << "\n";
        for (long long x : a)
            cout << x << " ";
        cout << "\n";
    }
    return 0;
}