책을 참고하여 문제를 풀어봤습니다.
계속 오답이 뜨는데 디버기을 해봐도 모르겠습니다 ㅜㅜ
어디가 문제인가요??

public class JLIS {

public static Scanner scan = new Scanner(System.in);
private static int[] A, B;
private static int[][] cache;

private static String[] result;

public static void main(String[] args) {

    int testNum = scan.nextInt();
    result = new String[testNum];

    for(int i=0; i<testNum; i++) {
        result[i] = "";
        int a = scan.nextInt();
        int b = scan.nextInt();
        A = new int[a];
        B = new int[b];
        cache = new int[a+1][b+1];

        for(int j=0; j<a; j++) {
            A[j] = scan.nextInt();
        }

        for(int k=0; k<b; k++) {
            B[k] = scan.nextInt();
        }

        int max = getLIS(-1, -1);
        if( max < 2) {
            max = 0;
        }
        result[i] = result[i].concat(max+"\n");
    }

    for(int i=0; i<testNum; i++) {
        System.out.print(result[i]);
    }

}

private static int getLIS(int aI, int bI) {
  int ret = cache[aI+1][bI+1];

  if(ret != 0) return ret;

  ret = 0;

  int a = (aI==-1 ? -1 : A[aI]);
  int b = (bI==-1 ? -1 : B[bI]);
  int max = Math.max(a, b);

  for(int nextA=aI+1; nextA<A.length; ++nextA) {
    if(max < A[nextA]) {
        ret = Math.max(ret, getLIS(nextA, bI)+1);
    }
  }
  for(int nextB=bI+1; nextB<B.length; ++nextB) {
    if(max < B[nextB]) {
        ret = Math.max(ret, getLIS(aI, nextB)+1);
    }
  }

  cache[aI+1][bI+1] = ret;
  return ret;

}

}