Word Subsets

You are given two string arrays words1 and words2.

A string b is a subset of string a if every letter in b occurs in a including multiplicity.

• For example, "wrr" is a subset of "warrior" but is not a subset of "world".

A string a from words1 is universal if for every string b in words2, b is a subset of a.

Return an array of all the universal strings in words1. You may return the answer in any order.

Example 1:

Input: words1 = ["amazon","apple","facebook","google","leetcode"], words2 = ["e","o"]
Output: ["facebook","google","leetcode"]

Example 2:

Input: words1 = ["amazon","apple","facebook","google","leetcode"], words2 = ["l","e"]
Output: ["apple","google","leetcode"]

Constraints:

• 1 <= words1.length, words2.length <= 104
• 1 <= words1[i].length, words2[i].length <= 10
• words1[i] and words2[i] consist only of lowercase English letters.
• All the strings of words1 are unique.

SOLUTION:

from collections import Counter

class Solution:
    def isSubset(self, ctr1, ctr2):
        for c in ctr1:
            if ctr2[c] < ctr1[c]:
                return False
        return True

    def wordSubsets(self, words1: List[str], words2: List[str]) -> List[str]:
        univ = Counter()
        for w in words2:
            curr = Counter(w)
            for c in curr:
                univ[c] = max(univ[c], curr[c])
        return [w for w in words1 if self.isSubset(univ, Counter(w))]