<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 Trie {
public:
    bool eow;
    Trie* nodes[26];

    Trie() {
        eow = false;
        for(auto &i : nodes) i = nullptr;
    }
    
    void insert(string word) {
        Trie* temp = this;

        for(auto ch : word)
        {
            int idx = ch - 'a';

            if(temp->nodes[idx] == nullptr) temp->nodes[idx] = new Trie();

            temp = temp->nodes[idx];
        }

        temp->eow = true;
    }
    
    bool search(string word) {
        Trie* temp = this;

        for(auto ch : word)
        {
            int idx = ch - 'a';

            if(temp->nodes[idx] == nullptr) return false;

            temp = temp->nodes[idx];
        }

        if(temp->eow == true) return true;

        return false;
    }
    
    bool startsWith(string prefix) {
        Trie* temp = this;

        for(auto ch : prefix)
        {
            int idx = ch - 'a';

            if(temp->nodes[idx] == nullptr) return false;

            temp = temp->nodes[idx];
        }

        return true;
    }
};

class Solution {
public:
    unordered_map<int, bool> memo;

    bool solve(Trie* root, string s, int start)
    {
        if (start == s.size()) return true;

        if (memo.find(start) != memo.end()) return memo[start];

        Trie* temp = root;

        for (int i = start; i < s.length(); ++i) 
        {
            int idx = s[i] - 'a';

            if (temp->nodes[idx] == nullptr) break;  

            temp = temp->nodes[idx];

            if (temp->eow && solve(root, s, i + 1)) return true;
        }

        return memo[start] = false;
    }

    bool wordBreak(string s, vector<string>& wordDict) {
        Trie* root = new Trie();

        for(auto str : wordDict) root->insert(str);

        return solve(root, s, 0);
    }
};
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