Length of a Linked List in Python

Suppose we have a singly linked list, we have to find its length. The linked list has fields next and val.

So, if the input is like [2 -> 4 -> 5 -> 7 -> 8 -> 9 -> 3], then the output will be 7.

To solve this, we will follow these steps −

• count := 0
• while node is non null, do
  • count := count + 1
  • node:= next of node
• return count

Let us see the following implementation to get better understanding −

Example

class ListNode:
   def __init__(self, data, next = None):
      self.val = data
      self.next = next
def make_list(elements):
   head = ListNode(elements[0])
   for element in elements[1:]:
      ptr = head
      while ptr.next:
         ptr = ptr.next
         ptr.next = ListNode(element)
   return head
class Solution:
   def solve(self, node):
      count = 0
      while node:
         count +=1
         node=node.next
      return count
ob = Solution()
head = make_list([2,4,5,7,8,9,3])
print(ob.solve(head))

Input

[2,4,5,7,8,9,3]

Output

7