<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 trie {
private:
    static const int MAX_CHAR = 26;
    trie* child[MAX_CHAR];
    bool isleaf {};

public:
    trie() {
         // set any array to 0s, here pointers to null
        memset(child, 0, sizeof(child));
    }

    void insert(string str, int idx = 0) {
        if (idx == (int) str.size())
            isleaf = 1;
        else {
            int cur = str[idx] - 'a';
            if(child[cur] == 0)
                child[cur] = new trie();
            child[cur] -> insert(str, idx + 1);
        }
    }

    void iterative_insert(string str) {
        trie* cur = this;

        for(int i = 0; i < (int) str.size(); ++i) {
            int ch = str[i] - 'a';

            if(!cur->child[ch])
                cur -> child[ch] = new trie();

            cur = cur -> child[ch];
        }
        cur->isleaf = true;
    }

    bool word_exist(string str, int idx = 0) {
        if (idx == (int) str.size())
            return isleaf ;

        int cur = str[idx] - 'a';
        if(!child[cur])
            return false;

        return child[cur] -> word_exist(str, idx + 1);
    }

    bool iterative_word_exist(string str) {
        trie* cur = this;

        for(int i=0; i<(int)str.size(); ++i) {
            int ch = str[i] - 'a';

            if(!cur->child[ch])
                return false;

            cur = cur -> child[ch];
        }
        return cur -> isleaf;
    }

    bool prefix_exist(string str, int idx = 0) {
        if (idx == (int) str.size())
            return true ;

        int cur = str[idx] - 'a';
        if(!child[cur])
            return false;

        return child[cur] -> word_exist(str, idx + 1);
    }

    string first_word_prefix(const string &str, int idx = 0, string res = "") {


        if(isleaf)
            return res;

        if (idx == (int) str.size())
            return res ;

        int cur = str[idx] - 'a';
        if(!child[cur])
            return str;

        return child[cur] -> first_word_prefix(str, idx + 1, res+str[idx]);
    }


};

class Solution {
    trie root;
public:
    void sol(vector<string>& dictionary){
        for(string i : dictionary)
            root.insert(i);
    }
    string replaceWords(vector<string>& dictionary, string sentence) {
        vector<string> words;
        stringstream ss(sentence);
        string word;

        sol(dictionary);

        while (ss >> word) {
            words.push_back(word);
        }
        string res;
        for(int i=0; i<(int)words.size(); ++i)
            res+= root.first_word_prefix(words[i]) + (i==(int)words.size()-1 ? "":" ");
        return res;
    }
};
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