feat(work): add solution for LeetCode 208 Implement Trie (Prefix Tree)

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

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