text: '''
  Author : MiKueen
  Level : Easy
  Problem Statement : Convert Binary Number in a Linked List to Integer
  
  Given head which is a reference node to a singly-linked list. The value of each node in the linked list is either 0 or 1. 
  The linked list holds the binary representation of a number.
  Return the decimal value of the number in the linked list.
  
  Example 1:
  Input: head = [1,0,1]
  Output: 5
  Explanation: (101) in base 2 = (5) in base 10
  
  Example 2:
  Input: head = [0]
  Output: 0
  
  Example 3:
  Input: head = [1]
  Output: 1
  
  Example 4:
  Input: head = [1,0,0,1,0,0,1,1,1,0,0,0,0,0,0]
  Output: 18880
  
  Example 5:
  Input: head = [0,0]
  Output: 0
  
  Constraints:
  The Linked List is not empty.
  Number of nodes will not exceed 30.
  Each node's value is either 0 or 1.
  '''
  
  # Definition for singly-linked list.
  # class ListNode:
  #     def __init__(self, val=0, next=None):
  #         self.val = val
  #         self.next = next
  
  class Solution:
      def getDecimalValue(self, head: ListNode) -> int:
          if head.next is None:
              return head.val
          
          # Method 1
          res = ''
          while head:
              res += str(head.val)
              head = head.next
          return int(res, 2)
      
          # Method 2 - Cool trick
          res = 0
          while head:
              res = 2 * res + head.val
              head = head.next
          return res
          