<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;
    bool isTerminal;
    TrieNode* children[26];                 // no. suffices ahead of that node

    TrieNode(char c){
        data=c;                             // node value
        isTerminal=false;                   // if the node is the last node
        for(int i=0;i<26;i++)
        children[i]=NULL;
    }
};
class Trie{
    public:
    TrieNode* root;
    Trie(){
        root = new TrieNode('\0');          // root node started with null char
    }
    void insertUtil(TrieNode* root, string word){
        if(word.length() == 0){                // word is inserted
            root->isTerminal=true;
            return;
        }

        int idx = word[0] - 'a';
        TrieNode* child;

        if(root->children[idx] != NULL)      // the char is already there
        child=root->children[idx];
        else{
            child = new TrieNode(word[0]);      // if not there
            root->children[idx] = child;
        }

        insertUtil(child, word.substr(1));      // one by one char is inserted
    }
    void insertWord(string word){
        insertUtil(root, word);
    }
    void searchUtil(TrieNode* root, string word, string &rep){
        if(word.length() == 0)
        return;

        int idx = word[0] - 'a';
        TrieNode* child;

        if(root->children[idx] == NULL)
        return;
        else{
            rep.push_back((char)(idx + 'a'));

            if(root->children[idx]->isTerminal)
            return;
            else
            child = root->children[idx];
        }

        searchUtil(child, word.substr(1), rep);
    }
    string searchWord(string word){
        string rep="";
        searchUtil(root, word, rep);
        return rep;
    }
};
class Solution {
public:
    string replaceWords(vector<string>& dictionary, string sentence) {
        Trie *t = new Trie();
        for(string str: dictionary)
        t->insertWord(str);

        stringstream ss(sentence);
        string ans="", word;
        while(ss >> word){
            string rep = t->searchWord(word);
            if(count(dictionary.begin(), dictionary.end(), rep))
            ans += " "+rep;
            else
            ans += " "+word;
        }
        return ans.substr(1);
    }
};
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