<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 val;
    trieNode* child[26];
    bool isTerminal;

    trieNode(int value){
        this->val = value;
        for(int i = 0; i < 26; i++){
            child[i] = NULL;
        }
        this->isTerminal = false;
    }
};


void insert(trieNode* root, string word, int i){
    // base case
    if(i >= word.size()){
        root->isTerminal = true;
        return;
    }

    char ch = word[i];
    int index = ch - 'a';
    trieNode* child;

    if(root->child[index] != NULL){
        child = root->child[index];
    }
    else{
        child = new trieNode(ch);
        root->child[index] = child;
    }
    insert(child, word, i+1);
}

string searchWord(trieNode* root, string word, int i){

    if(i >= word.size() ) return word;
    // base case
    if(root->isTerminal){
        return word.substr(0, i);
    }

    char ch = word[i];
    int index = ch-'a';
    trieNode* child;

    if(root->child[index] != NULL) child = root->child[index];
    else return word;

    string recAns = searchWord(child, word, i+1);
    return recAns;
}

class Solution {
public:
    string replaceWords(vector<string>& dictionary, string sentence) {
        trieNode* root = new trieNode('-');
        for(auto x: dictionary) insert(root, x, 0);

        stringstream s(sentence); 
        string word, res = ""; 
        while (s >> word){
            if(res != "") res += " ";
            res += searchWord(root, word, 0);
        }
        return res;
    }
};
234242