916. Word Subsets

 https://leetcode.com/problems/word-subsets/description/

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.

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Intuition

Brute force - For every word in words2 check if its a subset of word in words1

This work is repeated - words1.length * words2.length

For universal check we need to check if max character count is possible in word1

Pre compute the max freq of each character across all words in words 2

Finally check if freq of each char in word 1 covers max freq of each char in words 2

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Time - O(M + N)

Space - O(1)

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