<p>You are given two string arrays <code>words1</code> and <code>words2</code>.</p>

<p>A string <code>b</code> is a <strong>subset</strong> of string <code>a</code> if every letter in <code>b</code> occurs in <code>a</code> including multiplicity.</p>

<ul>
	<li>For example, <code>&quot;wrr&quot;</code> is a subset of <code>&quot;warrior&quot;</code> but is not a subset of <code>&quot;world&quot;</code>.</li>
</ul>

<p>A string <code>a</code> from <code>words1</code> is <strong>universal</strong> if for every string <code>b</code> in <code>words2</code>, <code>b</code> is a subset of <code>a</code>.</p>

<p>Return an array of all the <strong>universal</strong> strings in <code>words1</code>. You may return the answer in <strong>any order</strong>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> words1 = [&quot;amazon&quot;,&quot;apple&quot;,&quot;facebook&quot;,&quot;google&quot;,&quot;leetcode&quot;], words2 = [&quot;e&quot;,&quot;o&quot;]
<strong>Output:</strong> [&quot;facebook&quot;,&quot;google&quot;,&quot;leetcode&quot;]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> words1 = [&quot;amazon&quot;,&quot;apple&quot;,&quot;facebook&quot;,&quot;google&quot;,&quot;leetcode&quot;], words2 = [&quot;l&quot;,&quot;e&quot;]
<strong>Output:</strong> [&quot;apple&quot;,&quot;google&quot;,&quot;leetcode&quot;]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= words1.length, words2.length &lt;= 10<sup>4</sup></code></li>
	<li><code>1 &lt;= words1[i].length, words2[i].length &lt;= 10</code></li>
	<li><code>words1[i]</code> and <code>words2[i]</code> consist only of lowercase English letters.</li>
	<li>All the strings of <code>words1</code> are <strong>unique</strong>.</li>
</ul>

class Solution {
public:
    vector<string> wordSubsets(vector<string>& words1, vector<string>& words2) {
        int n1 = words1.size(), n2 = words2.size();
        vector< vector<int> > freq2Arr(n2, vector<int>(26, 0)); 

        for (int i = 0; i < n2; i++) {
            for (int j = 0; j < words2[i].length(); j++) 
                freq2Arr[i][(int)(words2[i][j] - 'a')]++;
        }
        
        vector<int> freq2(26, 0);
        for (int i = 0; i < n2; i++) {
            for (int j = 0; j < 26; j++) 
                freq2[j] = max(freq2Arr[i][j], freq2[j]);
        }

        vector<string> universals;

        for (int i = 0; i < n1; i++) {
            vector<int> freq1(26, 0);
            for (int j = 0; j < words1[i].length(); j++)
                freq1[(int)(words1[i][j] - 'a')]++;

            bool isUniversal = true;
            for (int k = 0; k < 26 && isUniversal; k++) {
                if (freq2[k] > freq1[k])
                    isUniversal = false;
            }
            if (isUniversal)
                universals.push_back(words1[i]);
        }

        return universals;
    }
};
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