Insert after another item in linked list in python

Question

I am trying to insert an item after another one but my code doesn't work. The below function insert_after_another doesn't work.

class LinkedList:
    def __init__(self):
        self.head = None

    def insert_end(self,data):
        x = Node(data)
        if self.head == None:
            self.head = x
            return
        temp = self.head
        while(temp.next != None):
            temp = temp.next
        temp.next = x

   def insert_after_another(self,old_data,new_data):
        t_old = Node(old_data)
        d_new = Node(new_data)
        temp = self.head
        while(temp):
            if temp.data == old_data:
                d_new.next = t_old.next
                t_old.next = d_new

            temp = temp.next

class Node:
    def __init__(self,data):
        self.data = data
        self.next = None


if __name__=='__main__':
    llist = LinkedList()
    llist.insert_end(3)
    llist.insert_end(32)
    llist.insert_after_another(3,13)

I am not getting any result when I try to print the data.

Fenil · Accepted Answer · 2019-06-27 06:40:48Z

1

d_new.next = t_old.next

in this line t_old.next pointing to nothing nor there is a pointer to it, it is just a node you created before.

def insert_after_another(self,old_data,new_data):
        d_new=Node(new_data)
        temp=self.head
        while(temp):
            if temp.data==old_data:
                d_new.next = temp.next
                temp.next = d_new
                break

This may work I think. You just need two swaps only, The new node should point the old node's next and the old node should point to the new one.

edited Jun 27, 2019 at 6:40

Fenil

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answered Jun 27, 2019 at 6:07

Maxx Selva K

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Comments

Josef · Accepted Answer · 2021-06-24 23:33:53Z

0

This will be able to resolve your problem. Consider having correct identations and renaming your method.

def insert_after_value(self, old_data, new_data):

    if self.head is None:
        return

    if self.head.data == old_data:
        self.head.next = Node(new_data, self.head.next)
        return

    temp = self.head

    while temp:
        if temp.data == old_data:
            temp.next = Node(new_data, temp.next)
            break

    temp = temp.next

edited Jun 24, 2021 at 23:33

Josef

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answered Jun 24, 2021 at 19:09

michael ditrick

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