Trie Data Structure

Author: jai2dev

Python/Data-Structures/Trie/trie.py

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+import sys
+
+# index of given char
+def index(inputCh):
+ return ord(inputCh) - ord('a')
+
+
+# empty Node
+class Node(object):
+ children = None
+
+ def __init__(self):
+ self.children = [None] * 26
+ self.ch = ' '
+ self.word = ""
+ self.isLeaf = False
+ self.parent = None
+
+
+class Trie(object):
+ root = None
+
+ def __init__(self):
+ self.root = Node()
+
+ def insertString(self, in_string):
+
+ current = self.root
+ for c in in_string[:-1]:
+ idx = index(c)
+ try:
+ if current.children[idx] is None:
+ current.children[idx] = Node()
+ current.children[idx].ch = c
+ current.children[idx].word = current.word + c
+ current.children[idx].parent = current
+ except IndexError as ie:
+ print("idx = {}\nchar = {}\nstring = {}".format(idx, c, in_string))
+
+ current = current.children[idx]
+ current.isLeaf = True
+
+ def searchString(self, in_string):
+
+ current = self.root
+
+ for c in in_string:
+ idx = index(c)
+
+ # if character is in the trie
+ if current.children[idx] is not None:
+ current = current.children[idx]
+
+ # character is not in the trie, word is not exist
+ else:
+ return False
+
+ # if word is in the trie, returns true
+ return current.isLeaf
+
+ def deleteString(self, in_string):
+
+ current = self.root
+ if self.searchString(in_string):
+ for c in in_string:
+ idx = index(c)
+ current = current.children[idx]
+
+ current.isLeaf = False
+
+
+
+
+# Examples
+
+if __name__ == '__main__':
+
+new_trie = Trie()
+
+
+# insertion
+new_trie.insertString("apple\n")
+new_trie.insertString('app\n')
+new_trie.insertString("application\n")
+new_trie.insertString("homework\n")
+
+# search
+print(new_trie.searchString("app")) # expected output: true
+print(new_trie.searchString("apply")) # expected output: false
+
+# delete
+new_trie.deleteString('app')
+
+# search after delete
+print(">>>Search after delete<<<")
+print(new_trie.searchString('app')) # expected output: false
+print(new_trie.searchString('application')) # expected output: true