Leetcode Changes

Leetcode/implement_trie_prefix_tree.py

@@ -0,0 +1,77 @@
+"""
+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
+"""
+
+
+class Trie(object):
+
+    def __init__(self):
+        self.trie = {}
+
+    def insert(self, word):
+        """
+        :type word: str
+        :rtype: None
+        """
+        trie = self.trie
+        for char in word:
+            if char not in trie:
+                trie[char] = {}
+            trie = trie[char]
+        trie["-"] = True
+
+    def search(self, word):
+        """
+        :param word:
+        :return:
+        """
+        trie = self.trie
+        for char in word:
+            if char not in trie:
+                return False
+            trie = trie[char]
+        return "-" in trie
+
+    def startsWith(self, word):
+        """
+        :param word:
+        :return:
+        """
+        trie = self.trie
+        for char in word:
+            if char not in trie:
+                return False
+            trie = trie[char]
+        return True
+
+
+t = Trie()
+t.insert("apple")
+print(t.trie)
+print(t.search("apple"))
+print(t.search("app"))