g0201_0300.s0208_implement_trie_prefix_tree

Class Trie

java.lang.Object

g0201_0300.s0208_implement_trie_prefix_tree.Trie

public class Trie
extends Object

208 - Implement Trie (Prefix Tree).

Medium

A trie (pronounced as “try”) or prefix tree 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.

Implement the Trie class:

• Trie() Initializes the trie object.
• void insert(String word) Inserts the string word into 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 only of lowercase English letters.
• At most 3 * 104 calls in total will be made to insert, search, and startsWith.

Constructor Summary

Constructors

Constructor and Description
Trie()

Method Summary

Modifier and Type	Method and Description
void	insert(String word)
boolean	search(String word)
boolean	search(String word, TrieNode root, int idx)
boolean	startsWith(String prefix)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Trie

public Trie()

Method Detail

insert

public void insert(String word)

search

public boolean search(String word)

search

public boolean search(String word,
                      TrieNode root,
                      int idx)

startsWith

public boolean startsWith(String prefix)