Hi, here’s your problem today. This problem was recently asked by AirBNB:

Implement auto-completion. Given a large set of words (for instance 1,000,000 words) and then a single word prefix, find all words that it can complete to.

class Solution:
  def build(self):
    # Fill this in.
    
  def autocomplete(self, word):
    # Fill this in.

s = Solution()
s.build(['dog', 'dark', 'cat', 'door', 'dodge'])
print(s.autocomplete('do'))
# ['dog', 'door', 'dodge']

Can you solve this optimally (in linear time with regards to the result set)?