message: update word-ladder.py
  Use ascii_lowercase
diff: # Time: O(n * d), n is length of string, d is size of dictionary
  # Space: O(d)
  +from string import ascii_lowercase
  +
  class Solution(object):
  def ladderLength(self, beginWord, endWord, wordList):
  @@ -18,7 +20,7 @@ class Solution(object):
  if word == endWord:
  return distance + 1
  for i in xrange(len(word)):
  - for j in 'abcdefghijklmnopqrstuvwxyz':
  + for j in ascii_lowercase:
  candidate = word[:i] + j + word[i+1:]
  if candidate not in visited and candidate in lookup:
  next_queue.append(candidate)
  @@ -27,5 +29,3 @@ class Solution(object):
  cur = next_queue
  return 0
  -
  -
  