<p>Given a string <code>s</code>, return <em>the </em><span data-keyword="lexicographically-smaller-string"><em>lexicographically smallest</em></span> <span data-keyword="subsequence-string"><em>subsequence</em></span><em> of</em> <code>s</code> <em>that contains all the distinct characters of</em> <code>s</code> <em>exactly once</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;bcabc&quot;
<strong>Output:</strong> &quot;abc&quot;
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;cbacdcbc&quot;
<strong>Output:</strong> &quot;acdb&quot;
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 1000</code></li>
	<li><code>s</code> consists of lowercase English letters.</li>
</ul>

<p>&nbsp;</p>
<strong>Note:</strong> This question is the same as 316: <a href="https://leetcode.com/problems/remove-duplicate-letters/" target="_blank">https://leetcode.com/problems/remove-duplicate-letters/</a>
class Solution:
    def find_shortest_lexical(self, x):
        full_chars = set(x)
        if len(full_chars) == 1:
            return x[0]
        min_char, min_char_pos = 'z', 0
        for i in range(len(x)):
            if set(x[i:]) == full_chars:
                if x[i] < min_char:
                    min_char = x[i]
                    min_char_pos = i
        if set(x[min_char_pos:]) == full_chars:
            return min_char + self.find_shortest_lexical(x[min_char_pos+1:].replace(min_char,''))
    def smallestSubsequence(self, s: str) -> str:
         return self.find_shortest_lexical(s)
16600