LeetCode-in-All

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.

Solution

var Trie = function() {
    this.root = {};
};

/** 
 * @param {string} word
 * @return {void}
 */
Trie.prototype.insert = function(word) {
    let node = this.root;
    for (const char of word) {
        if (!node[char]) {
            node[char] = {};
        }
        node = node[char];
    }
    node.isWord = true;
};

/** 
 * @param {string} word
 * @return {boolean}
 */
Trie.prototype.search = function(word) {
    let node = this.root;
    for (const char of word) {
        if (!node[char]) {
            return false;
        }
        node = node[char];
    }
    return node.isWord === true;
};

/** 
 * @param {string} prefix
 * @return {boolean}
 */
Trie.prototype.startsWith = function(prefix) {
    let node = this.root;
    for (const char of prefix) {
        if (!node[char]) {
            return false;
        }
        node = node[char];
    }
    return true;
};

/** 
 * Your Trie object will be instantiated and called as such:
 * var obj = new Trie()
 * obj.insert(word)
 * var param_2 = obj.search(word)
 * var param_3 = obj.startsWith(prefix)
 */

export { Trie }

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