<p>A <ahref="https://en.wikipedia.org/wiki/Trie"target="_blank"><strong>trie</strong></a> (pronounced as "try") or <strong>prefix tree</strong> is a tree data structure used to efficiently store and retrieve keys in a dataset of strings. There are various applications of this data structure, such as autocomplete and spellchecker.</p>
<p>Implement the Trie class:</p>
<ul>
<li><code>Trie()</code> Initializes the trie object.</li>
<li><code>void insert(String word)</code> Inserts the string <code>word</code> into the trie.</li>
<li><code>boolean search(String word)</code> Returns <code>true</code> if the string <code>word</code> is in the trie (i.e., was inserted before), and <code>false</code> otherwise.</li>
<li><code>boolean startsWith(String prefix)</code> Returns <code>true</code> if there is a previously inserted string <code>word</code> that has the prefix <code>prefix</code>, and <code>false</code> otherwise.</li>
<li><code>word</code> and <code>prefix</code> consist only of lowercase English letters.</li>
<li>At most <code>3 * 10<sup>4</sup></code> calls <strong>in total</strong> will be made to <code>insert</code>, <code>search</code>, and <code>startsWith</code>.</li>
