<p>Given a string array <code>words</code>, return <em>an array of all characters that show up in all strings within the </em><code>words</code><em> (including duplicates)</em>. 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> words = ["bella","label","roller"]
<strong>Output:</strong> ["e","l","l"]
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> words = ["cool","lock","cook"]
<strong>Output:</strong> ["c","o"]
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= words.length &lt;= 100</code></li>
	<li><code>1 &lt;= words[i].length &lt;= 100</code></li>
	<li><code>words[i]</code> consists of lowercase English letters.</li>
</ul>

class Solution {
public:
    vector<string> commonChars(vector<string>& words) {
        vector <pair<int, int>> occurrences(128, make_pair(0, INT_MAX)); // <num_words, max_occurs>
        unordered_map <char, int> chars;
        unordered_set <char> _occurs;
        for (string & word : words) {
            chars.clear();
            for (char & chr : word) {
                if (chars.find(chr) == chars.end())
                    chars[chr] = 0;
                chars[chr]++;
            }
            for (auto & [chr, occ] : chars) {
                occurrences[chr].second = std::min(occurrences[chr].second, occ);
                occurrences[chr].first++;
                _occurs.insert(chr);
            }
        }
        vector <string> occurs;
        int j, m = words.size();
        for (char chr : _occurs)
            if (occurrences[chr].first == m)
                for (j = 0; j < occurrences[chr].second; ++j)
                    occurs.push_back(std::string({chr, '\0'}));
        return occurs;
    }
};
14000