<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:
    char data;
    vector<TrieNode*> children;
    bool isTerminal;

    TrieNode(char data) {
        this->data = data;
        this->children = vector<TrieNode*>(26, NULL);
        this->isTerminal = false;
    }
};

class Trie {
private:
    TrieNode* root;

    bool insertUtil(TrieNode* node, string &word, int idx) {
        int n = word.size();
        if (idx == n) {
            node->isTerminal = true;
            return true;
        }
        
        int pos = word[idx] - 'a';
        if (node->children[pos] == NULL) {
            node->children[pos] = new TrieNode(word[idx]);
        }

        return node->isTerminal && insertUtil(node->children[pos], word, idx + 1);
    }

public:
    Trie() {
        this->root = new TrieNode('\0');
        this->root->isTerminal = true;
    }

    bool insert(string &word) {
        return insertUtil(root, word, 0);
    }
};

bool comp(string &s1, string &s2) {
    if (s1.size() == s2.size()) {
        return s1 > s2;
    }
    return s1.size() < s2.size();
}

class Solution {
public:
    string longestWord(vector<string>& words) {
        Trie dictionary;

        sort(words.begin(), words.end(), comp);

        string ans;
        for (auto &word : words) {
            if (dictionary.insert(word)) {
                ans = word;
            }
        }

        return ans;
    }
};
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