Paper over Keyboard

So, I completed a HackerRank problem this morning to work my brain back into shape for upcoming interviews. The problem is titled The Minion Game, and the lesson I learned while completing this problem was measure twice, cut once, aka I didn’t spend enough time thinking about the problem before programming.

Working out a programming problem on paper first will help you solve it most of the time.

hackerrank.com/challenges/the-minion-game/problem


Question

Kevin and Stuart want to play the ‘The Minion Game’.

Game Rules

Both players are given the same string, S. Both players have to make substrings using the letters of the string S. Stuart has to make words starting with consonants. Kevin has to make words starting with vowels. The game ends when both players have made all possible substrings.

Scoring

A player gets +1 point for each occurrence of the substring in the string S.

For Example:

String S = BANANA Kevin’s vowel beginning word = ANA Here, ANA occurs twice in BANANA. Hence, Kevin will get 2 Points.

Working Answer

Here is my final, tidy answer that runs in O(n). The single calculation score = (string_len - iletter) was previously completed by breaking the substring into a set of smaller substrings and counting them with a for loop. After sitting back, pondering the question, and understanding that this larger calculation was unneccesary (terrible original answer in next section,) my algorithm improved to O(n) time and was able to run in the time limit imposed by HackerRank.

def minion_game(string):
    string_len = len(string)
    stuart = 0
    kevin = 0

    for iletter in range(string_len):
        score = (string_len - iletter)
        if string[iletter] in ['A','E','I','O','U']:
            kevin = kevin + score
        else:
            stuart = stuart + score

    if stuart > kevin:
        print("Stuart " + str(stuart))
    elif kevin > stuart:
        print("Kevin " + str(kevin))
    else:
        print("Draw")

Original Answer

This answer kept failing because it took far too long. It runs in O(n^2) and originally used four loops, three more than the working answer.

def v(word):
    if word[0] in ['A','E','I','O','U']:
        return True
    else:
        return False

def minion_game(string):

    substrings = []
    substrings_vowels = []
    string_len = len(string)

    for iletter in range(string_len):
        for isubletter in range(iletter+1, string_len+1):
            substring = string[iletter:isubletter]
            if v(substring):
                if substring not in substrings_vowels:
                    substrings_vowels.append(substring)
            elif substring not in substrings:
                substrings.append(substring)


    # Stuart - Consonants
    print("\nStuart")
    stuart = score(string, substrings)

    # Kevin - Vowels

    print("\nKevin")
    kevin = score(string, substrings_vowels)

    if stuart > kevin:
        print("Stuart " + str(stuart))
    elif kevin > stuart:
        print("Kevin " + str(kevin))
    else:
        print("Draw")

def score(original_string, list_of_strings):
    total = 0
    for item in sorted(list_of_strings):
        icount = original_string.count(item)
        print("{} : {}".format(item,icount))
        total = total + icount

    return total

HR Snippet:

if __name__ == '__main__':
    s = input()
    minion_game(s

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