Longest Common Subsequence

You are given a sequence $A=[A_1,A_2,\cdots,A_N]$ of length $N$ and a sequence $B=[B_1,B_2,\cdots,B_M]$ of length $M$.

Print any longest common subsequence of $A$ and $B$. A subsequence is obtained by deleting zero or more elements from a sequence while preserving the order of the remaining elements.

The input is given in the following format:

$T$ $\mathrm{case}_1$ $\mathrm{case}_2$ $\vdots$ $\mathrm{case}_T$

Each case is given in the following format:

$N\ M$ $A_1\ A_2\ \cdots\ A_N$ $B_1\ B_2\ \cdots\ B_M$

For each case, print the length $K$ of a longest common subsequence on one line. If $K>0$, print its $K$ elements separated by spaces on the next line. If $K=0$, print no elements.

If several longest common subsequences exist, you may print any of them.

• $1\leq T\leq100\,000$.
• $1\leq N,M\leq2000$.
• $-10^9\leq A_i\leq10^9$ ($1\leq i\leq N$).
• $-10^9\leq B_j\leq10^9$ ($1\leq j\leq M$).
• The sum of $N+M$ over all cases is at most $200\,000$.
• The sum of $NM$ over all cases is at most $4\,000\,000$.