1290-Convert-Binary-Number-in-a-Linked-List-to-Integer.py

'''
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.

The most significant bit is at the head of the linked list.
'''

# 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:
        result = 0
        
        while head:
            result = result * 2 + head.val
            head = head.next
                
        return result