problem208

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208. Implement Trie (Prefix Tree) (Medium)

Trie (we pronounce "try") or prefix tree is a tree data structure used to retrieve a key in a strings dataset. There are various applications of this very efficient data structure, such as autocomplete and spellchecker.

Implement the Trie class:

• Trie() initializes the trie object.
• void insert(String word) inserts the string word to the trie.
• boolean search(String word) returns true if the string word is in the trie (i.e., was inserted before), and false otherwise.
• boolean startsWith(String prefix) returns true if there is a previously inserted string word that has the prefix prefix, and false otherwise.

 

Example 1:

Input
["Trie", "insert", "search", "search", "startsWith", "insert", "search"]
[[], ["apple"], ["apple"], ["app"], ["app"], ["app"], ["app"]]
Output
[null, null, true, false, true, null, true]

Explanation
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

 

Constraints:

• 1 <= word.length, prefix.length <= 2000
• word and prefix consist of lowercase English letters.
• At most 3 * 104 calls will be made to insert, search, and startsWith.

Related Topics

[Design] [Trie]

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