<p>Given an array of strings <code>words</code>, return <em>the words that can be typed using letters of the alphabet on only one row of American keyboard like the image below</em>.</p>

<p>In the <strong>American keyboard</strong>:</p>

<ul>
	<li>the first row consists of the characters <code>&quot;qwertyuiop&quot;</code>,</li>
	<li>the second row consists of the characters <code>&quot;asdfghjkl&quot;</code>, and</li>
	<li>the third row consists of the characters <code>&quot;zxcvbnm&quot;</code>.</li>
</ul>
<img alt="" src="https://assets.leetcode.com/uploads/2018/10/12/keyboard.png" style="width: 800px; max-width: 600px; height: 267px;" />
<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> words = [&quot;Hello&quot;,&quot;Alaska&quot;,&quot;Dad&quot;,&quot;Peace&quot;]
<strong>Output:</strong> [&quot;Alaska&quot;,&quot;Dad&quot;]
</pre>

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

<pre>
<strong>Input:</strong> words = [&quot;omk&quot;]
<strong>Output:</strong> []
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> words = [&quot;adsdf&quot;,&quot;sfd&quot;]
<strong>Output:</strong> [&quot;adsdf&quot;,&quot;sfd&quot;]
</pre>

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

<ul>
	<li><code>1 &lt;= words.length &lt;= 20</code></li>
	<li><code>1 &lt;= words[i].length &lt;= 100</code></li>
	<li><code>words[i]</code> consists of English letters (both lowercase and uppercase).&nbsp;</li>
</ul>

auto init = []() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    return 0;
}();
class Solution {
public:
    vector<string> findWords(vector<string>& words) {
        string row_1 = "qwertyuiopQWERTYUIOP";
        string row_2 = "asdfghjklASDFGHJKL";
        string row_3 = "zxcvbnmZXCVBNM";
        unordered_set<char> set_1 = {row_1.begin(), row_1.end()};
        unordered_set<char> set_2 = {row_2.begin(), row_2.end()};
        unordered_set<char> set_3 = {row_3.begin(), row_3.end()};

        vector<string> res;
        for (int i = 0; i < words.size(); i++) {
            bool Row_1 = true;
            bool Row_2 = true;
            bool Row_3 = true;
            for (int j = 0; j < words[i].size(); j++) {
                if (!set_1.contains(words[i][j])) {
                    Row_1 = false;
                }
                if (!set_2.contains(words[i][j])) {
                    Row_2 = false;
                }
                if (!set_3.contains(words[i][j])) {
                    Row_3 = false;
                }
            }
            if (Row_1 || Row_2 || Row_3) {
                res.push_back(words[i]);
            }
        }
        return res;
    }
};
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