Search for an Element in Linked List without Recursion in Python

When it is required to search for an element in a linked list without using recursion method, a method to add values to the linked list, as well as a method to display the elements of a Linked List.

It would also have a method that helps find the index of the element that is being searched.

Below is a demonstration for the same −

Example

 Live Demo

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

class my_linked_list:
   def __init__(self):
      self.head = None
      self.last_node = None

   def add_value(self, my_data):
      if self.last_node is None:
         self.head = Node(my_data)
         self.last_node = self.head
      else:
         self.last_node.next = Node(my_data)
         self.last_node = self.last_node.next

   def print_it(self):
      curr = self.head
      while curr is not None:
         print(curr.data)
         curr = curr.next

   def find_index_val(self, my_key):
      curr = self.head

      index_val = 0
      while curr:
         if curr.data == my_key:
            return index_val
         curr = curr.next
         index_val = index_val + 1
      return -1

my_instance = my_linked_list()
my_list = [67, 4, 78, 98, 32, 0, 11, 8]
for data in my_list:
   my_instance.add_value(data)
print('The linked list is : ')
my_instance.print_it()
print()

my_key = int(input('What value would you search for? '))
index_val = my_instance.find_index_val(my_key)
if index_val == -1:
   print(str(my_key) + ' was not found.')
else:
   print('Element was found at index ' + str(index_val) + '.')
n = int(input('How many elements would you wish to add ? '))
for i in range(n):
   data = int(input('Enter data : '))
   my_instance.add_value(data)
print('The linked list is : ')
my_instance.print_it()

Output

The linked list is :
67
4
78
98
32
0
11
8
What value would you search for? 11
Element was found at index 6.
How many elements would you wish to add ? 2
Enter data : 111
Enter data : 56
The linked list is :
67
4
78
98
32
0
11
8
111
56

Explanation

• The ‘Node’ class is created.

• Another ‘my_linked_list’ class with required attributes is created.

• It has an ‘init’ function that is used to initialize the first element, i.e the ‘head’ to ‘None’ and last node to ‘None’.

• Another method named ‘add_value’ is defined, that is used to add data to the linked list.

• Another method named ‘print_it’ is defined that is used to display the linked list data on the console.

• Another method named ‘find_index_val’ is defined that helps find the index of the element entered by the user.

• An object of the ‘my_linked_list’ class is created.

• A list is defined.

• This list is iterated over, and the methods are called on it to add data.

• This is displayed on the console using the ‘print_it’ method.

• The user input is asked for the element to be searched.

• The ‘find_index_val’ method is called on this, and output is displayed on the console.