Squash commit

utilities/trie.py

@@ -0,0 +1,80 @@
+class Trie(object):
+    def __init__(self):
+        """
+        Initialize your data structure here.
+        """
+        self.d = {}
+
+    def insert(self, word):
+        """
+        Inserts a word into the trie.
+        :type word: str
+        :rtype: void
+        """
+        curr = self.d
+        for char in word:
+            if char not in curr:
+                curr[char] = {}
+            curr = curr[char]
+        curr['#'] = {} # Using an empty dict rather than a boolean value makes recursive traversal easier.
+
+    def search(self, word):
+        """
+        Returns if the word is in the trie.
+        :type word: str
+        :rtype: bool
+        """
+        curr = self.d
+        for char in word:
+            if char in curr:
+                curr = curr[char]
+            else:
+                return False
+        return '#' in curr
+
+    def startsWith(self, prefix):
+        """
+        Returns if there is any word in the trie that starts with the given prefix.
+        :type prefix: str
+        :rtype: bool
+        """
+        curr = self.d
+        for char in prefix:
+            if char in curr:
+                curr = curr[char]
+            else:
+                return False
+        return True
+
+    def searchRegex(self, word):
+        """
+        Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter.
+        :type word: str
+        :rtype: bool
+        """
+        def traverse(node, index):
+            if len(word) == index:
+                return '#' in node
+            char = word[index]
+            if char == '.':
+                for key in node.keys():
+                    if traverse(node[key], index+1):
+                        return True
+                return False
+            else:
+                if char not in node:
+                    return False
+                return traverse(node[char], index + 1)
+        return traverse(self.d, 0)
+
+# Example
+trie = Trie()
+trie.insert('hello')
+print(trie.search('hello') == True)
+print(trie.startsWith('hello') == True)
+print(trie.startsWith('hel') == True)
+print(trie.search('world') == False)
+print(trie.startsWith('wor') == False)
+print(trie.searchRegex('..llo') == True)
+print(trie.searchRegex('..llx') == False)
+print(trie.searchRegex('..') == False)