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

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def getDecimalValue(self, head: ListNode) -> int:
        res = 0
        while head:
            res = res*2 + head.val
            head = head.next
        return res