leetcode/work/1/Medium/Hash Table/208.implement-trie-prefix-tree.py

"""
208. Implement Trie (Prefix Tree)
Difficulty: Medium
https://leetcode.com/problems/implement-trie-prefix-tree/

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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 * 10^4 calls in total will be made to insert, search,
and startsWith.
"""


class TrieNode:
    def __init__(self):
        self.children = {}
        self.endOfWord = False


class Trie:
    def __init__(self):
        self.root = TrieNode()

    def insert(self, word: str) -> None:
        cur = self.root

        for c in word:
            if c not in cur.children:
                cur.children[c] = TrieNode()
            cur = cur.children[c]
        cur.endOfWord = True

    def search(self, word: str) -> bool:
        cur = self.root

        for c in word:
            if c not in cur.children:
                return False
            cur = cur.children[c]

        return cur.endOfWord

    def startsWith(self, prefix: str) -> bool:
        cur = self.root

        for c in prefix:
            if c not in cur.children:
                return False
            cur = cur.children[c]

        return True


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