<p>Given an array of strings <code>words</code> representing an English Dictionary, return <em>the longest word in</em> <code>words</code> <em>that can be built one character at a time by other words in</em> <code>words</code>.</p>

<p>If there is more than one possible answer, return the longest word with the smallest lexicographical order. If there is no answer, return the empty string.</p>

<p>Note that the word should be built from left to right with each additional character being added to the end of a previous word.&nbsp;</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> words = [&quot;w&quot;,&quot;wo&quot;,&quot;wor&quot;,&quot;worl&quot;,&quot;world&quot;]
<strong>Output:</strong> &quot;world&quot;
<strong>Explanation:</strong> The word &quot;world&quot; can be built one character at a time by &quot;w&quot;, &quot;wo&quot;, &quot;wor&quot;, and &quot;worl&quot;.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> words = [&quot;a&quot;,&quot;banana&quot;,&quot;app&quot;,&quot;appl&quot;,&quot;ap&quot;,&quot;apply&quot;,&quot;apple&quot;]
<strong>Output:</strong> &quot;apple&quot;
<strong>Explanation:</strong> Both &quot;apply&quot; and &quot;apple&quot; can be built from other words in the dictionary. However, &quot;apple&quot; is lexicographically smaller than &quot;apply&quot;.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= words.length &lt;= 1000</code></li>
	<li><code>1 &lt;= words[i].length &lt;= 30</code></li>
	<li><code>words[i]</code> consists of lowercase English letters.</li>
</ul>

class Node{
private:
    Node*links[26];
    bool flag=false;

public:
    bool containsKey(char ch){
        return links[ch-'a']!=NULL;
    }
    void add(char ch,Node*node){
        links[ch-'a']=node;
    }
    Node* get(char ch){
        return links[ch-'a'];
    }
    void setEnd(){
        flag=true;
    }
    bool isEnd(){
        return flag;
    }
};
class Trie{
public:
    Node*root;
    Trie(){
        root=new Node();
    }
    void insert(string str){
        Node*node=root;
        for(auto it:str){
            if(!node->containsKey(it))
                node->add(it,new Node());
            node=node->get(it);
        }
        node->setEnd();
    }
   bool isAns(string str) {
    Node* node = root;
    for(auto it : str) {
        if(!node->containsKey(it) || !node->get(it)->isEnd())
            return false;
        node = node->get(it);
    }
    return true; 
}

};
class Solution {
public:
    string longestWord(vector<string>& words) {
        Trie trie;
        for(auto it:words)
            trie.insert(it);
        
        string ans = "";
        for(auto word: words) {
            if(trie.isAns(word)) {
                if(word.size() > ans.size()) {
                    ans = word;
                } else if(word.size() == ans.size()) {
                    ans = min(ans, word);
                }
            }
        }

        return ans;
    }
};
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