这道题的细节还是挺多的。大题思路就是对于当前的 $b_i$，如果 $a_i$ 还没有确定，那么令 $a_i = b_i$，这样可以留出 $a_{i + 1}$ 的位置给 $b_{i + 1}$ 确定。如果 $a_{i}$ 已经确定，检查它是否恰好等于 $b_{i}$，如果不等，那么只能让 $a_{i + 1} = b_i$。接下来如果 $b_i < b_{i + 1}$，同时 $a_i = b_i$，此时 $a_{i+1}$ 这个位置就「没有用了」，不妨令 $a_{i + 1} = 0$，原因是 $a_{i + 1}$ 不能等于 $b_{i + 1}$（如果 $a_{i + 1} = b_{i + 1}$，那么 $b_{i} = b_{i + 1}$，然而 $b_i < b_{i + 1}$）。

// Date: Fri Dec  8 19:17:03 2023

#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>

#include <algorithm>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>

using namespace std;

const int INF = 0x3f3f3f3f, MOD = 1e9 + 7;
const double eps = 1e-8;
const int dir[8][2] = {
    {0, 1}, {0, -1}, {1, 0}, {-1, 0}, {1, 1}, {1, -1}, {-1, 1}, {-1, -1},
};

typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> VI;
typedef pair<int, int> PII;

const ull Pr = 131;

#define For(i, a, b) for (int i = int(a); i < int(b); ++i)
#define Rof(i, a, b) for (int i = int(b) - 1; i >= int(a); --i)
#define For1(i, a, b) for (int i = int(a); i <= int(b); ++i)
#define Rof1(i, a, b) for (int i = int(b); i >= int(a); --i)
#define ForE(i, j) for (int i = h[j]; i != -1; i = ne[i])

#define f1 first
#define f2 second
#define pb push_back
#define has(a, x) (a.find(x) != a.end())
#define nonempty(a) (!a.empty())
#define all(a) (a).begin(), (a).end()
#define SZ(a) int((a).size())

#ifdef _DEBUG
#define debug1(x) cout << #x " = " << x << endl;
#define debug2(x, y) cout << #x " = " << x << " " #y " = " << y << endl;
#define debug3(x, y, z)                                                        \
  cout << #x " = " << x << " " #y " = " << y << " " #z " = " << z << endl;
#else
#define debug1
#define debug2
#define debug3
#endif

const int N = 200010;

int t, n, a[N], b[N];

int main(void) {
#ifdef _DEBUG
  freopen("1811c.in", "r", stdin);
#endif
  std::ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);

  cin >> t;

  while (t--) {
    int n1;
    cin >> n;

    n1 = n - 1;

    For1(i, 1, n1) { cin >> b[i]; }

    memset(a, -1, sizeof a);

    For1(i, 1, n1) {
      bool flag = false;

      if (a[i] == -1) {
        a[i] = b[i];
        flag = true;
      } else {
        if (a[i] < b[i]) {
          a[i + 1] = b[i];
        } else {
          flag = true;
        }
      }

      if (b[i] < b[i + 1]) {
        if (flag) {
          a[i + 1] = 0;
          if (i + 2 <= n) {
            a[i + 2] = b[i + 1];
          }
        }
      }
    }

    if (a[n] == -1)
      a[n] = 0;

    For1(i, 1, n) { cout << a[i] << ' '; }
    cout << '\n';
  }

  return 0;
}