<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>

class TrieNode{
    public:
        char data;
        unordered_map<char, TrieNode*> children;
        bool isTerminal;
    
        TrieNode(char data){
            this->data = data;
            isTerminal = false;
        }
};

class Solution {
public:
    TrieNode* root = new TrieNode('-');
    void insertWords(TrieNode* root, string word){
        if(word.length() == 0){
            root->isTerminal = true;
            return;
        }

        char ch = word[0];
        TrieNode* child;
        if(root->children.find(ch) != root->children.end()){
            child = root->children[ch];
        }
        else{
            child = new TrieNode(ch);
            root->children[ch] = child;
        }
        insertWords(child, word.substr(1));
    }

    bool searchWord(TrieNode* root, string word, string& output){
        if(root->isTerminal){
            return true;
        }

        if(word.length() == 0){
            return false;
        }

        TrieNode* child;
        char ch = word[0];
        if(root->children.find(ch) != root->children.end()){
            child = root->children[ch];
            output.push_back(child->data);
        }
        else{
            return false;
        }
        return searchWord(child, word.substr(1), output);
    }

    string replaceWords(vector<string>& dictionary, string sentence) {
        for(string w : dictionary){
            insertWords(root, w);
        }

        string ans;
        int start = 0, end = 0;

        while(end < sentence.length()){
            if(sentence[end] == ' ' || end == sentence.length() -1){
                int len = end == sentence.length() - 1 ? sentence.size() : end - start;
                string word = sentence.substr(start, len);
                string tempOutput="";
                bool found = searchWord(root, word, tempOutput);
                ans+= !found ? word : tempOutput;
                if(sentence[end] == ' '){
                    ans+= " ";
                }
                start = end + 1;
            }
            end++;
        }
        return ans;
    }
};
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