Question

Hello everyone, I have some trouble in ps6 problem 3. I don't know how to change the complexity of is_valid_word from O(len(word_list)) to O(1) by change the arguments.

Answer 1

use a dictionary??
http://wiki.python.org/moin/TimeComplexity

Answer 2

Using a dictionary is exactly the right idea. Recall that the dictionary works using hashing which allows us to search in constant time. Think about changing the input of is_valid_word from word_list to a dictionary such as points_dict .