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0208-implement-trie-prefix-tree/README.md

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+<h2><a href="https://leetcode.com/problems/implement-trie-prefix-tree/">208. Implement Trie (Prefix Tree)</a></h2><h3>Medium</h3><hr><div><p>A <a href="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>
+</ul>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre style="position: relative;"><strong>Input</strong>
+["Trie", "insert", "search", "search", "startsWith", "insert", "search"]
+[[], ["apple"], ["apple"], ["app"], ["app"], ["app"], ["app"]]
+<strong>Output</strong>
+[null, null, true, false, true, null, true]
+
+<strong>Explanation</strong>
+Trie trie = new Trie();
+trie.insert("apple");
+trie.search("apple");   // return True
+trie.search("app");     // return False
+trie.startsWith("app"); // return True
+trie.insert("app");
+trie.search("app");     // return True
+<div class="open_grepper_editor" title="Edit &amp; Save To Grepper"></div></pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= word.length, prefix.length &lt;= 2000</code></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>
+</ul>
+</div>