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40 lines
2.1 KiB
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<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>
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<p>Implement the Trie class:</p>
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<ul>
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<li><code>Trie()</code> Initializes the trie object.</li>
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<li><code>void insert(String word)</code> Inserts the string <code>word</code> into the trie.</li>
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<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>
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<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>
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</ul>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input</strong>
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["Trie", "insert", "search", "search", "startsWith", "insert", "search"]
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[[], ["apple"], ["apple"], ["app"], ["app"], ["app"], ["app"]]
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<strong>Output</strong>
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[null, null, true, false, true, null, true]
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<strong>Explanation</strong>
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Trie trie = new Trie();
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trie.insert("apple");
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trie.search("apple"); // return True
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trie.search("app"); // return False
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trie.startsWith("app"); // return True
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trie.insert("app");
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trie.search("app"); // return True
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>1 <= word.length, prefix.length <= 2000</code></li>
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<li><code>word</code> and <code>prefix</code> consist only of lowercase English letters.</li>
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<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>
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</ul>
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