916. Word Subsets

leetcode_916.java

/*
916. Word Subsets

Medium

Companies
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 <= 10^4
* 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.
*/

class Solution {
    public List<String> wordSubsets(String[] words1, String[] words2) {
        int[] fq = new int[26];
        for (String w : words2) {
            int[] curr_fq = fq(w);
            for (int i = 0; i < 26; i++) {
                fq[i] = Math.max(fq[i], curr_fq[i]);
            }
        }
        List<String> result = new LinkedList<>();
        for (String w : words1) {
            int[] curr_fq = fq(w);
            boolean to_add = true;
            for (int i = 0; i < 26; i++) {
                if (fq[i] > 0 && curr_fq[i] < fq[i]) {
                    to_add = false;
                }
            }
            if (to_add) {
                result.add(w);
            }
        }
        return result;
    }
    private int[] fq(String s) {
        int[] fq = new int[26];
        for (int i = 0; i < s.length(); i++) {
            fq[s.charAt(i)-'a']++;
        }
        return fq;
    } 
}