<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 TrieNode {
    public: 
    unordered_map<char, TrieNode*> children;
    bool isWord = false;
    char val;
    TrieNode() {}
    TrieNode (char v) { this->val = v;
    }
};
class Trie {
private :
TrieNode * root;
public: 
Trie() {
    root = new TrieNode();
}
void insert(string word) {
    TrieNode * tmp =root;
    for(char c: word) {
        if(tmp->children.find(c) == tmp->children.end()) {
            tmp->children[c] = new TrieNode(c);
        }
        tmp = tmp->children[c];
    }
    tmp->isWord  =  true;
}
bool isOrdered(string word) {
    TrieNode * tmp = root;
    for(char c: word) {
        if(tmp==root || tmp->isWord) {
            tmp = tmp->children[c];
            continue;
        }
        return false;
    }
    return true;
}
};

class Solution {
public:
    string longestWord(vector<string>& words) {
        Trie * search = new Trie();
        string curr("");
        int size = 0;
        for(string s: words) {
            search->insert(s);
        }
        for(string str: words) {
            if(search->isOrdered(str) && size<=str.size()){
                curr =(size ==str.size()) ? min(curr, str): str;
                size = str.size();
 }        }
 return curr;
    }
};
33503