<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>

struct TrieNode {
    TrieNode* child[26] = {nullptr};
    bool end = false;
};

class Solution {
public:
    string longestWord(vector<string>& words) {
        sort(words.begin(), words.end(), [](auto &a, auto &b){
            return a.size() < b.size();
        });
        TrieNode* root = new TrieNode();
        string ans;
        for (auto& s : words) {
            auto* curr = root;
            int count = 0;
            for (auto& c : s) {
                int i = c - 'a';
                if (!curr->child[i]) {
                    curr->child[i] = new TrieNode(); 
                } 
                curr = curr->child[i];
                count += curr->end;
            } 
            curr->end = true;
            count += curr->end;
            if (count == s.size()) {
                if (s.size() > ans.size()) {
                    ans = s;
                } else if (s.size() == ans.size() && s < ans) {
                    ans = s;
                }
            }
        }
        return ans;
    }
};

auto boom = [](){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    return 0;
}();
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