# Auto-complete feature using Trie

AlgorithmsAnalysis of AlgorithmsData Structure Algorithms

We have a Trie, and when a user enters a character, we have to show the matching string the Trie. This feature we call it as auto-completion. For example, if a Trie contains "xyzzzz,""xyz," "xxxyyxzzz" and when the user enter xy, then we have to show them xyzzzz, xyz, etc..,

Steps to achieve the result.

• Search for the string using the standard Trie algorithm.

• If the string is not present, then return -1.

• If the string is present and is the end of a word in Trie, then print the string.

• If the matching string doesn't have any node, then return.

• Else print all the nodes.

Let's start coding.

# class for Trie Node
class TrieNode():
def __init__(self):
# initialising trie node
self.trie_node = {}
self.last_node = False
class Trie():
def __init__(self):
# initialising the trie
self.root = TrieNode()
# list to store the words
self.words = []
def create_trie(self, keys):
# creating the Trie using data
for key in keys:
# inserting one key to the trie
self.insert_node(key)
def insert_node(self, key):
node = self.root
for obj in list(key):
if not node.trie_node.get(obj):
# creating a TrieNode
node.trie_node[obj] = TrieNode()
node = node.trie_node[obj]
# making leaf node
node.last_node = True
def search(self, key):
# searching for the key
node = self.root
is_found = True
for obj in list(key):
if not node.trie_node.get(obj):
is_found = False
break
node = node.trie_node[obj]
return node and node.last_node and is_found
def matches(self, node, word):
if node.last_node:
self.words.append(word)
for obj, n in node.trie_node.items():
self.matches(n, word + obj)
def show_auto_completion(self, key):
node = self.root
is_found = False
temp = ''
for obj in list(key):
# checking the word
if not node.trie_node.get(obj):
is_found = True
break
temp += obj
node = node.trie_node[obj]
if is_found:
return 0
elif node.last_node and not node.trie_node:
return -1
self.matches(node, temp)
for string in self.words:
print(string)
return 1
# data for the Trie
strings = ["xyz", "xyzzzz", "xyabad", "xyyy", "abc", "abbccc", "xyx", "xyxer",
a"]
# word for auto completion
string = "xy"
# instantiating Trie class
trie = Trie()
# creating Trie using the strings
trie.create_trie(strings)
# getting the auto completion words for the string from strings
result = trie.show_auto_completion(string)
if result == -1 or result == 0:
print("No matches")

If you run the above code, you will get the following result.

xyz
xyzzzz
xyxer