Returns the length of the Longest Common Subsequence between two seqs.

  Source: http://www.algorithmist.com/index.php/Longest_Common_Subsequence

  Args:
    x: sequence of words
    y: sequence of words

  Returns
    integer: Length of LCS between x and y

def _len_lcs(x, y):
  """Returns the length of the Longest Common Subsequence between two seqs.

  Source: http://www.algorithmist.com/index.php/Longest_Common_Subsequence

  Args:
    x: sequence of words
    y: sequence of words

  Returns
    integer: Length of LCS between x and y
  """
  table = _lcs(x, y)
  n, m = len(x), len(y)
  return table[n, m]