<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 {

    struct TreeNode{
        TreeNode *ch[26]={};
        bool exist;
    };

    TreeNode* root=new TreeNode();

    void implement(string word){
        TreeNode* curr=root;

        for(int i=0;i<word.size();i++){
            int ad=word[i]-'a';
            if(curr->ch[ad]==NULL){
                curr->ch[ad]=new TreeNode();
            }
            curr=curr->ch[ad];
        }
        curr->exist=true;
    }

    int derivative(string word){
        TreeNode* curr=root;
        for(int i=0;i<word.size();i++){
            int c=word[i]-'a';

            if(curr->ch[c]==NULL){
                return -1;
            }
            curr=curr->ch[c];
            if(curr->exist){
                return i;
            }
        }
        return word.size()-1;
    }

public:
    string replaceWords(vector<string>& dictionary, string sentence) {
        for(auto word: dictionary){
            implement(word);
        }
        sentence=sentence;
        string word,ans;
        for(int i=0;i<sentence.size();i++){
            if(sentence[i]==' ' ){
                int ind=derivative(word);
                ans = wordMake(word,ans,ind);
                word="";
            }else{
                word+=sentence[i];
            }
            
        }
        if (word.size()>0){
            int ind =derivative(word);
            ans = wordMake(word,ans,ind);
        }
        return ans;
    }

    string wordMake(string word, string ans,int ind){
        if(ind!=-1){
                if(ans.size()==0){
                    ans+=word.substr(0,ind+1);
                }else{
                    ans+=" "+word.substr(0,ind+1);
                }
            }else{
                if(ans.size()==0){
                    ans+=word;
                }else{
                    ans+=" "+word;
                }  
        }
        return ans;
    }
};
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