Most Common Word.py

# Given a paragraph and a list of banned words, return the most frequent word that is not in the
# list of banned words.  It is guaranteed there is at least one word that isn't banned, and that the answer is unique.
#
# Words in the list of banned words are given in lowercase, and free of punctuation.
# Words in the paragraph are not case sensitive.  The answer is in lowercase.

# Input:
# paragraph = "Bob hit a ball, the hit BALL flew far after it was hit."
# banned = ["hit"]
# Output: "ball"
# Explanation:
# "hit" occurs 3 times, but it is a banned word.
# "ball" occurs twice (and no other word does), so it is the most frequent non-banned word in the paragraph.
# Note that words in the paragraph are not case sensitive,
# that punctuation is ignored (even if adjacent to words, such as "ball,"),
# and that "hit" isn't the answer even though it occurs more because it is banned.

import collections


class Solution:
    def mostCommonWord(self, paragraph, banned):
        for c in "!?',;.":
            paragraph = paragraph.replace(c, " ")
        dict = collections.Counter(paragraph.lower().split())

        ans = ""
        num = 0
        for word in dict:
            if dict[word] > num and word not in banned:
                ans = word
                num = dict[word]

        return ans