Merge pull request #1 from Brahanyaa98/Brahanyaa98-patch-1

Create trie.py

Author: Brahanyaa98

trie.py

@@ -0,0 +1,84 @@
+
+from typing import Tuple
+
+
+class TrieNode(object):
+    """
+    Our trie node implementation. Very basic. but does the job
+    """
+    
+    def __init__(self, char: str):
+        self.char = char
+        self.children = []
+        # Is it the last character of the word.`
+        self.word_finished = False
+        # How many times this character appeared in the addition process
+        self.counter = 1
+    
+
+def add(root, word: str):
+    """
+    Adding a word in the trie structure
+    """
+    node = root
+    for char in word:
+        found_in_child = False
+        # Search for the character in the children of the present `node`
+        for child in node.children:
+            if child.char == char:
+                # We found it, increase the counter by 1 to keep track that another
+                # word has it as well
+                child.counter += 1
+                # And point the node to the child that contains this char
+                node = child
+                found_in_child = True
+                break
+        # We did not find it so add a new chlid
+        if not found_in_child:
+            new_node = TrieNode(char)
+            node.children.append(new_node)
+            # And then point node to the new child
+            node = new_node
+    # Everything finished. Mark it as the end of a word.
+    node.word_finished = True
+
+
+def find_prefix(root, prefix: str) -> Tuple[bool, int]:
+    """
+    Check and return 
+      1. If the prefix exsists in any of the words we added so far
+      2. If yes then how may words actually have the prefix
+    """
+    node = root
+    # If the root node has no children, then return False.
+    # Because it means we are trying to search in an empty trie
+    if not root.children:
+        return False, 0
+    for char in prefix:
+        char_not_found = True
+        # Search through all the children of the present `node`
+        for child in node.children:
+            if child.char == char:
+                # We found the char existing in the child.
+                char_not_found = False
+                # Assign node as the child containing the char and break
+                node = child
+                break
+        # Return False anyway when we did not find a char.
+        if char_not_found:
+            return False, 0
+    # Well, we are here means we have found the prefix. Return true to indicate that
+    # And also the counter of the last node. This indicates how many words have this
+    # prefix
+    return True, node.counter
+
+if __name__ == "__main__":
+    root = TrieNode('*')
+    add(root, "hackathon")
+    add(root, 'hack')
+
+    print(find_prefix(root, 'hac'))
+    print(find_prefix(root, 'hack'))
+    print(find_prefix(root, 'hackathon'))
+    print(find_prefix(root, 'ha'))
+    print(find_prefix(root, 'hammer'))