Package g0201_0300.s0208_implement_trie_prefix_tree

Class 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 Detail

      • Trie

        public Trie()

    • Method Detail

      • insert

        public void insert​(String word)

      • search

        public boolean search​(String word)

      • search

        public boolean search​(String word,
                      g0201_0300.s0208_implement_trie_prefix_tree.Trie.TrieNode root,
                      int idx)

      • startsWith

        public boolean startsWith​(String prefix)