<p>Given a string <code>s</code> and a dictionary of strings <code>wordDict</code>, return <code>true</code> if <code>s</code> can be segmented into a space-separated sequence of one or more dictionary words.</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;leetcode&quot;, wordDict = [&quot;leet&quot;,&quot;code&quot;]
<strong>Output:</strong> true
<strong>Explanation:</strong> Return true because &quot;leetcode&quot; can be segmented as &quot;leet code&quot;.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;applepenapple&quot;, wordDict = [&quot;apple&quot;,&quot;pen&quot;]
<strong>Output:</strong> true
<strong>Explanation:</strong> Return true because &quot;applepenapple&quot; can be segmented as &quot;apple pen apple&quot;.
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> false
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 300</code></li>
	<li><code>1 &lt;= wordDict.length &lt;= 1000</code></li>
	<li><code>1 &lt;= wordDict[i].length &lt;= 20</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>
</ul>

class Solution {
public:
    bool wordBreak(string s, vector<string>& wordDict) {
        std::vector<bool> visited(s.size(), false);
        std::unordered_set<std::string> words;
        for (const auto& word : wordDict) {
            words.insert(word);
        }
        auto result = false;
        
        Helper(s, visited, words, result);
        
        return result;
    }
    
    void Helper(std::string& s, 
                std::vector<bool>& visited, 
                const std::unordered_set<std::string>& words,
                bool& found) {
        if (found) return;
        if (visited[s.size()]) return;
        visited[s.size()] = true;
        
        if (words.count(s)) {
            found = true;
            return;
        }
        
        std::string other{s.back()};
        s.pop_back();
        
        while (!s.empty()) {
            if (words.count(other)) {
                Helper(s, visited, words, found);
            }
            other = s.back() + other;
            s.pop_back();
        }
        
        std::swap(s, other);
    }
};
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