input: Write a function to find the longest common subsequence of two strings. If one of the strings is empty, return an empty string. The function should return the longest common subsequence as a string.
  
  
  def find_lcs(x, y):
      # Implementation of the function
      pass
  
  assert find_lcs("abcdaf", "acbcf") == "abcf"
  assert find_lcs("abcdef", "ghijkl") == ""
  assert find_lcs("hello", "helo") == "helo"
  assert find_lcs("python", "typhon") == "python"
  assert find_lcs("", "hello") == ""
  
output: def find_lcs(x, y):
      if not x or not y:
          return ""
      m, n = len(x), len(y)
      dp = [[""] * (n + 1) for _ in range(m + 1)]
      for i in range(1, m + 1):
          for j in range(1, n + 1):
              if x[i - 1] == y[j - 1]:
                  dp[i][j] = dp[i - 1][j - 1] + x[i - 1]
              else:
                  dp[i][j] = max(dp[i - 1][j], dp[i][j - 1], key=len)
      return dp[m][n]