Longest Word in Dictionary
<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>
Trie; Array; Hash Table; String; Sorting
/**
 * @param {string[]} words
 * @return {string}
 */
var longestWord = function (words) {
    const trie = new Trie();
    for (const w of words) {
        trie.insert(w);
    }

    let ans = '';
    for (const w of words) {
        if (trie.search(w) && (ans.length < w.length || (ans.length === w.length && w < ans))) {
            ans = w;
        }
    }
    return ans;
};

class Trie {
    constructor() {
        this.children = Array(26).fill(null);
        this.isEnd = false;
    }

    insert(w) {
        let node = this;
        for (let i = 0; i < w.length; i++) {
            const idx = w.charCodeAt(i) - 'a'.charCodeAt(0);
            if (node.children[idx] === null) {
                node.children[idx] = new Trie();
            }
            node = node.children[idx];
        }
        node.isEnd = true;
    }

    search(w) {
        let node = this;
        for (let i = 0; i < w.length; i++) {
            const idx = w.charCodeAt(i) - 'a'.charCodeAt(0);
            if (node.children[idx] === null || !node.children[idx].isEnd) {
                return false;
            }
            node = node.children[idx];
        }
        return true;
    }
}
