<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) {
        const int LETTER_NUM = 26;
        vector<int> common_freq(LETTER_NUM, INT_MAX);
        for (string& s : words)
        {
            vector<int> cur_freq(LETTER_NUM, 0);
            for (char c : s)
                ++cur_freq[c - 'a'];
            for (int i = 0; i < LETTER_NUM; ++i)
                common_freq[i] = min(common_freq[i], cur_freq[i]);
        }
        vector<string> res;
        for (int i = 0; i < LETTER_NUM; ++i)
            res.insert(res.end(), common_freq[i], string(1, 'a' + i));
        return res;
    }
};
12100