<p>In English, we have a concept called <strong>root</strong>, which can be followed by some other word to form another longer word - let&#39;s call this word <strong>derivative</strong>. For example, when the <strong>root</strong> <code>&quot;help&quot;</code> is followed by the word <code>&quot;ful&quot;</code>, we can form a derivative <code>&quot;helpful&quot;</code>.</p>

<p>Given a <code>dictionary</code> consisting of many <strong>roots</strong> and a <code>sentence</code> consisting of words separated by spaces, replace all the derivatives in the sentence with the <strong>root</strong> forming it. If a derivative can be replaced by more than one <strong>root</strong>, replace it with the <strong>root</strong> that has <strong>the shortest length</strong>.</p>

<p>Return <em>the <code>sentence</code></em> after the replacement.</p>

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

<pre>
<strong>Input:</strong> dictionary = [&quot;cat&quot;,&quot;bat&quot;,&quot;rat&quot;], sentence = &quot;the cattle was rattled by the battery&quot;
<strong>Output:</strong> &quot;the cat was rat by the bat&quot;
</pre>

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

<pre>
<strong>Input:</strong> dictionary = [&quot;a&quot;,&quot;b&quot;,&quot;c&quot;], sentence = &quot;aadsfasf absbs bbab cadsfafs&quot;
<strong>Output:</strong> &quot;a a b c&quot;
</pre>

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

<ul>
	<li><code>1 &lt;= dictionary.length &lt;= 1000</code></li>
	<li><code>1 &lt;= dictionary[i].length &lt;= 100</code></li>
	<li><code>dictionary[i]</code> consists of only lower-case letters.</li>
	<li><code>1 &lt;= sentence.length &lt;= 10<sup>6</sup></code></li>
	<li><code>sentence</code> consists of only lower-case letters and spaces.</li>
	<li>The number of words in <code>sentence</code> is in the range <code>[1, 1000]</code></li>
	<li>The length of each word in <code>sentence</code> is in the range <code>[1, 1000]</code></li>
	<li>Every two consecutive words in <code>sentence</code> will be separated by exactly one space.</li>
	<li><code>sentence</code> does not have leading or trailing spaces.</li>
</ul>


struct TrieNode
{
   
    std::unordered_map<char, TrieNode*> children;
    bool isEnd;
    TrieNode(): isEnd(false){}
    ~ TrieNode()
    {
        for (auto it = children.begin(); it != children.end(); ++it)
        {
            delete it->second;
        }
    }
};
class Trie {
public:
    Trie() {
        root = new TrieNode();
    }
    ~Trie()
    {
        delete root;
    }
    
    void insert(string word) {
        TrieNode* node = root;
        for (auto c : word)
        {
            if (node->children.find(c) == node->children.end())
            {
                node->children[c] = new TrieNode();
            }
            node = node->children[c];
        }
        node->isEnd = true;
        
    }
    
    bool search(string word) {
        TrieNode* node = root;
        for (auto c: word)
        {
            if (node->children.find(c) == node->children.end())
            {
                return false;
            }
            node = node->children[c];
        }
        return node->isEnd;
    }
    
    bool startsWith(string prefix) {
        TrieNode* node = root;
        for (auto c: prefix)
        {
            if (node->children.find(c) == node->children.end())
            {
                return false;
            }
            node = node->children[c];
        }
        return true;

        
    }
    TrieNode* root;
};

class Solution {
public:
    string replaceWords(vector<string>& dictionary, string sentence) {
    Trie*  mydict = new Trie();
    for (const auto& word : dictionary)
    {
        mydict->insert(word);
    }

    std::string res;

    std::istringstream iss(sentence);
    std::string word;
    while (iss >> word)
    {
        std::string prefix;
        for (auto c: word)
        {
            prefix += c;
            if (mydict->search(prefix))
            {
                break;
            }
        }
        res += prefix + " ";
    }

    res.pop_back(); // because of extra space at the end
    return res;        
    }
};
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