<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 Trie{
      public:
        Trie**children;
        bool flag;
        Trie(){
            flag = false;
            children = new Trie*[26];
            for(int i=0;i<26;i++){
                children[i] = NULL;
            }
        }
    };
    Trie * head = NULL;
    void insert(string s){
        Trie*root = head;
        for(int i=0;i<s.size();i++){
            int c = s[i]-'a';
            if(root->children[c]==NULL)
                root->children[c] = new Trie();
            root = root->children[c];
        }
        root->flag = true;
    }
    string getRoot(string temp){
        Trie* root = head;
        string ans = "";
       // cout<<temp<<endl;
        for(int i=0;i<temp.size();i++){
             int c = temp[i]-'a';
            // cout<<"c "<<temp[i]<<endl;
            if(root->flag){
                return ans;
            }
            else if(root->children[c]==NULL){
                 if(root->flag)
                    return ans;
                else
                    return temp;
            } 
            ans = ans + temp[i];
            root = root->children[c];
        }
        return ans;
    }
    string replaceWords(vector<string>& dic, string sentence) {
        head = new Trie();
        for(int i=0;i<dic.size();i++){
            insert(dic[i]);
        }
        int i =0;
        string answer ="", curr = "";
        while(i<=sentence.size()){
            if(i==sentence.size() || sentence[i]==' '){
                answer = answer + getRoot(curr);
                while(i<sentence.size() && sentence[i]==' ')
                    answer = answer + sentence[i],i++;
                if(i<sentence.size())
                curr = sentence[i];
                else
                curr = "";
            }else{
                curr+=sentence[i];
            }
            i++;
        }
        return answer;
        
    }
};
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