<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) {
        int words_size = words.size();
        vector<int> commonCharacterCounts(26), currentCharacterCounts(26);
        vector<string> result;

        for (char& ch : words[0]) {
            commonCharacterCounts[ch - 'a']++;
        }

        for (int i = 1; i < words_size; i++) {
            fill(currentCharacterCounts.begin(), currentCharacterCounts.end(),
                 0);

            for (char& ch : words[i]) {
                currentCharacterCounts[ch - 'a']++;
            }

            for (int letter = 0; letter < 26; letter++) {
                commonCharacterCounts[letter] =
                    min(commonCharacterCounts[letter],
                        currentCharacterCounts[letter]);
            }
        }

        for (int letter = 0; letter < 26; letter++) {
            for (int commonCount = 0;
                 commonCount < commonCharacterCounts[letter]; commonCount++) {
                result.push_back(string(1, letter + 'a'));
            }
        }

        return result;
    }
};
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