<p>Given a string <code>s</code> and a dictionary of strings <code>wordDict</code>, add spaces in <code>s</code> to construct a sentence where each word is a valid dictionary word. Return all such possible sentences in <strong>any order</strong>.</p>

<p><strong>Note</strong> that the same word in the dictionary may be reused multiple times in the segmentation.</p>

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

<pre>
<strong>Input:</strong> s = &quot;catsanddog&quot;, wordDict = [&quot;cat&quot;,&quot;cats&quot;,&quot;and&quot;,&quot;sand&quot;,&quot;dog&quot;]
<strong>Output:</strong> [&quot;cats and dog&quot;,&quot;cat sand dog&quot;]
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;pineapplepenapple&quot;, wordDict = [&quot;apple&quot;,&quot;pen&quot;,&quot;applepen&quot;,&quot;pine&quot;,&quot;pineapple&quot;]
<strong>Output:</strong> [&quot;pine apple pen apple&quot;,&quot;pineapple pen apple&quot;,&quot;pine applepen apple&quot;]
<strong>Explanation:</strong> Note that you are allowed to reuse a dictionary word.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;catsandog&quot;, wordDict = [&quot;cats&quot;,&quot;dog&quot;,&quot;sand&quot;,&quot;and&quot;,&quot;cat&quot;]
<strong>Output:</strong> []
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 20</code></li>
	<li><code>1 &lt;= wordDict.length &lt;= 1000</code></li>
	<li><code>1 &lt;= wordDict[i].length &lt;= 10</code></li>
	<li><code>s</code> and <code>wordDict[i]</code> consist of only lowercase English letters.</li>
	<li>All the strings of <code>wordDict</code> are <strong>unique</strong>.</li>
	<li>Input is generated in a way that the length of the answer doesn&#39;t exceed&nbsp;10<sup>5</sup>.</li>
</ul>

class Solution {
public:
    bool acceptance(unsigned int i, unsigned int j)
    {
        for (const auto& letter : words[j])
        {
            if (letter != letters[i])
                return false;
            ++i;
        }
        return true;
    }
    void search(unsigned int i)
    {
        if (i > size)
            return;
        if (i == size)
        {
            y.pop_back();
            searched.push_back(y);
            return;
        }
        for (unsigned int j = 0; j < sizeWords; ++j)
            if (acceptance(i, j))
            {
                unsigned int size = y.size();
                y.append(words[j]);
                y.push_back(' ');
                search(i + words[j].size());
                while (y.size() > size)
                    y.pop_back();
            }
    }
    vector<string> wordBreak(string letters, vector<string>& words)
    {
        this->letters = letters, this->words = words;
        size = this->letters.size(), sizeWords = this->words.size();
        search(0);
        return searched;
    }
private:
    unsigned int size, sizeWords;
    std::string letters, y;
    std::vector<std::string> searched, words;
};
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