why the pointer is not incrementing at line 27

Question

i am implementing the trie data structure, why my pointer is not incrementing at line# 27. all the characters are getting into forst node only.
this is my code

class Trienode:
    data:str
    next:list = [None]*26
    isTerminal:bool = False

    def __init__(self,data):
        self.data = data


class Trie:

    def __init__(self):
        self.root  = Trienode('#')

    def insert(self,data):
        
        temp = self.root

        for ch in data:
            index = ord(ch)- ord('a')
            # print(temp.next[index])
            if temp.next[index]==None:
               
                temp.next[index] = Trienode(ch)
                temp = temp.next[index]
            
            else:
                temp = temp.next[index]
        temp.isTerminal = True

    def display(self):
        temp = self.root
        for i in range(26):
            print(temp.next[i])


if  __name__=='__main__':
    root = Trie()
    root.insert("apple")
    root.insert("pineapple")

    root.display()

This is the output on console i am printing the pointer array of first node
console output

i tried the same logic to increment pointer in Linkedlist it is working fine.

Asked By: Mohammad Avesh Husain

||

Source

Answer 1

I’ve modified your sample a little bit.
Relevant changes are highlighted with a comment

class Trienode:
    def __init__(self, data):
        self.data: str = data
        self.next: list = [None] * 26
        self.isTerminal: bool = False

    def __str__(self):  # get more info on display
        return f"{self.data} - {''.join(str(n) for n in self.next if n is not None)}"

    def __repr__(self):  # appears nicely in my IDE ;)
        return f'Trienode({self.data})'


class Trie:

    def __init__(self):
        self.root = Trienode('#')

    def insert(self, data):

        temp = self.root

        for ch in data:
            index = ord(ch) - ord('a')
            if temp.next[index] is None:  # error was there I guess
                temp.next[index] = Trienode(ch)
            temp = temp.next[index]  # and here also
        temp.isTerminal = True

    def display(self):
        self._display(self.root)

    def _display(self, node):  # must use a recursion to display all the children
        print(node)
        for child in node.next:
            if child is not None:
                self._display(child)



if __name__ == '__main__':
    root = Trie()
    root.insert("apple")
    root.insert("pineapple")

    root.display

Hope this helps

Answered By: slouchart

why the pointer is not incrementing at line 27

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