#P1364B. Most socially-distanced subsequence

    ID: 5401 Type: RemoteJudge 1000ms 256MiB Tried: 0 Accepted: 0 Difficulty: (None) Uploaded By: Tags>greedytwo pointers*1300

Most socially-distanced subsequence

No submission language available for this problem.

Description

Given a permutation pp of length nn, find its subsequence s1s_1, s2s_2, \ldots, sks_k of length at least 22 such that:

  • s1s2+s2s3++sk1sk|s_1-s_2|+|s_2-s_3|+\ldots+|s_{k-1}-s_k| is as big as possible over all subsequences of pp with length at least 22.
  • Among all such subsequences, choose the one whose length, kk, is as small as possible.

If multiple subsequences satisfy these conditions, you are allowed to find any of them.

A sequence aa is a subsequence of an array bb if aa can be obtained from bb by deleting some (possibly, zero or all) elements.

A permutation of length nn is an array of length nn in which every element from 11 to nn occurs exactly once.

The first line contains an integer tt (1t21041 \le t \le 2 \cdot 10^4) — the number of test cases. The description of the test cases follows.

The first line of each test case contains an integer nn (2n1052 \le n \le 10^5) — the length of the permutation pp.

The second line of each test case contains nn integers p1p_1, p2p_2, \ldots, pnp_{n} (1pin1 \le p_i \le n, pip_i are distinct) — the elements of the permutation pp.

The sum of nn across the test cases doesn't exceed 10510^5.

For each test case, the first line should contain the length of the found subsequence, kk. The second line should contain s1s_1, s2s_2, \ldots, sks_k — its elements.

If multiple subsequences satisfy these conditions, you are allowed to find any of them.

Input

The first line contains an integer tt (1t21041 \le t \le 2 \cdot 10^4) — the number of test cases. The description of the test cases follows.

The first line of each test case contains an integer nn (2n1052 \le n \le 10^5) — the length of the permutation pp.

The second line of each test case contains nn integers p1p_1, p2p_2, \ldots, pnp_{n} (1pin1 \le p_i \le n, pip_i are distinct) — the elements of the permutation pp.

The sum of nn across the test cases doesn't exceed 10510^5.

Output

For each test case, the first line should contain the length of the found subsequence, kk. The second line should contain s1s_1, s2s_2, \ldots, sks_k — its elements.

If multiple subsequences satisfy these conditions, you are allowed to find any of them.

Samples

Sample Input 1

2
3
3 2 1
4
1 3 4 2

Sample Output 1

2
3 1 
3
1 4 2

Note

In the first test case, there are 44 subsequences of length at least 22:

  • [3,2][3,2] which gives us 32=1|3-2|=1.
  • [3,1][3,1] which gives us 31=2|3-1|=2.
  • [2,1][2,1] which gives us 21=1|2-1|=1.
  • [3,2,1][3,2,1] which gives us 32+21=2|3-2|+|2-1|=2.

So the answer is either [3,1][3,1] or [3,2,1][3,2,1]. Since we want the subsequence to be as short as possible, the answer is [3,1][3,1].