<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 Solution {
public:
class trieNode{
    public:
    char ch;
    trieNode* children[26];
    bool isTerminal;
    trieNode(char val){
        this->ch = val;
        for(int i=0;i<26;i++){
            children[i] =  NULL;
        }
        this->isTerminal = false;
    }
};

void insertword(trieNode* root, string word){
    // base case
    if(word.size() == 0){
        root->isTerminal = true;
        return;
    }
    char ch = word[0];
    int index = ch - 'a';
    trieNode* child;
    if(root->children[index] != NULL){
        // this char is already present in the trie so traverse
        child = root->children[index];
    }
    else{
        // this char is not present so create a node
        child = new trieNode(ch);
        root->children[index] = child;
    }

    insertword(child,word.substr(1));
}

void ispresent(trieNode* root, string word,bool &ans){
    if(word.length() == 0){
        ans = root->isTerminal?true:false;
        return;
    }
    char ch = word[0];
    int index = ch-'a';
    if(root->children[index] !=NULL){
        // that ch is present
        ispresent(root->children[index],word.substr(1),ans);
    }
    else{
        ans = false;
        return;
    }
}
void deleteword(trieNode* root, string word){
    // base case
    if(word.length() == 0){
        root->isTerminal = false;
        return;
    }
    char ch = word[0];
    int index = ch -'a';
    trieNode* child;
    if(root->children[index]!= NULL){
        child = root->children[index];
    }
    else{
        //not present;
        return;
    }
    deleteword(root->children[index],word.substr(1));
}
void check(trieNode* root , string str,int &i){
    if(root->isTerminal == true){
        return;
    }
    if(str.length() == 0){
        i=0;
        return;
    }
    char ch = str[0];
    int index = ch - 'a';
    if(root->children[index] != NULL){
        i++;
        check(root->children[index],str.substr(1),i);
    }
    else{
        i = 0;
        return;
    }
}
    string replaceWords(vector<string>& dictionary, string sentence) {
        trieNode* root = new trieNode('-');
        // inserting prefix into the trie
        for(int i = 0;i<dictionary.size();i++){
            insertword(root,dictionary[i]);
        }

        string str = "";
        string ans = "";

        for(int i =0;i<sentence.length();i++){

            if(sentence[i]!=' '){
            str += sentence[i];
            }

            else{
                // one word is complete int str
                int i = 0;
                check(root,str,i);
                if(i == 0){
                    // nahi mila common character
                    ans+=str;
                    ans+=" ";
                    str = "";
                }
                else{
                    string temp = str.substr(0,i);
                    ans+=temp;
                    ans+=" ";
                    str ="";
                }

               
            }
        }
        int i=0;
        check(root,str,i);
         if(i == 0){
                    // nahi mila common character
                    ans+=str;
                }
                else{
                    string temp = str.substr(0,i);
                    ans+=temp;  
                }
        return ans;
    }
};
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