Thanks for including the video link to the MIT lecture.

Is there any way to report this problem ? It's checker doesnt work. I have correct code and it fails on even first test case and they are the same.

i am getting correct output in sample case as 3 4 1 but getting some command error as

Error in command /custom-RB1ptiIaeNCmJhh5eUdH/solution errno = 2

Looks like there is some issue with this test case, Please fix the backend checker. I have similar problem as @nesamani and others.

Could someone say me why I have this error, please?: though the output is same but compilation message shows wrong answer and what is custom checker error message it shows: Error in command /custom-KY8ZmYAHCVNTfclUPusO/solution errno = 2

Python 3 solution, using dynamic program with a two dimensional table the size of the input arrays to store the length of longest subsequence, then trace back from the last square in the table to see where the matches where and eventually print all these matches (reversed) - that's the longest subsequence

input()
a = [0] + [int(x) for x in input().split()] # to make first row/col of 0's
b = [0] + [int(x) for x in input().split()]
# table will be the dynamic programming table
table = [[0 for _ in range(len(a))] for _ in range(len(b))]
# populating table
for i in range(1,len(b)):
  for j in range(1,len(a)):
    if a[j] == b[i]:
      table[i][j] = table[i-1][j-1] + 1
    else:
      table[i][j] = max(table[i][j-1], table[i-1][j])

# table[len(b)-1][len(a)-1] is the length of longest common subsequence
# in order to find the subsequence we have to trace back from that square
# see where the matches where and add them to word common_subsequence
length = table[len(b)-1][len(a)-1]
common_subsequence = []
curr = len(b)-1,len(a)-1 # save my current index in table in the search
while length:
  if b[curr[0]] == a[curr[1]]: # match - belongs to common subseq
    common_subsequence.append(b[curr[0]])
    length -= 1
    curr = (curr[0]-1,curr[1]-1)
  else: # go to the square that has longer subsequence until now
    if table[curr[0]-1][curr[1]] > table[curr[0]][curr[1]-1]:
      curr = (curr[0]-1,curr[1])
    else:
      curr = (curr[0],curr[1]-1)

print(' '.join(str(x) for x in common_subsequence[::-1])) # reverse

The checker is still not yet fixed :-/

The problem description says Sample Output is 1 2 3. Although my program outputs 1 2 3 it still can't pass the test.

I tried removing the tailing newline character but still no luck. Perhaps the checker does not work?

showing wrong answer for 1 2 3 for the sample test case , for the case 2 my output is 3 9 9 9 7 0 which is one of the longest sequence but it is only checking (3 3 9 9 7 0) (second test case - 9 10 3 9 8 3 9 7 9 7 0 3 3 9 9 9 1 7 2 0 6 )

Boys, there is some problem with the solution checker, it does not accept valid outputs. Please check it!

During "Run code" I get the following in "Custom Checker Error Message" field:

Error in command /custom-ZLzyY9MbLvo731KOX9bk/solution errno = 2

Also all tests fails.