<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>

#include <unordered_map>

class Solution {
public:
    vector<string> commonChars(vector<string>& words) {
        // key = 1
        // letter = c
        // value = 1
        std::vector<std::vector<size_t>> letters_count_by_word;

        for (auto & word : words) {
            std::vector<size_t> buf(28,0);
            // for(auto i : buf){
            //     std::cout << i << std::endl;
            // }
            for (auto & letter : word) {
                // std::cout << letter << " " << (letter - 'a') << std::endl;
                ++buf[letter - 'a'];
            }
            letters_count_by_word.push_back(buf);           
        }

        std::vector<string> output;
        for( int8_t i = 0; i < 28; ++i  ) {
            size_t min_value = letters_count_by_word[0][i];
            for(auto& vec : letters_count_by_word ){
                if (vec[i]< min_value ) {
                    min_value = vec[i];
                }
            }
            for (size_t z = 0; z < min_value; ++z){
                output.push_back({char(i+'a')});
            }
        }
        return output;
    }
};
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