leetcode1290

class Solution:
    def getDecimalValue(self, head: ListNode) -> int:
        res = 0
        lists = []
        while head != None:
            lists.append(head.val)
            head = head.next
        pos = 0
        for i in range(len(lists)-1,-1,-1):
            res += lists[i] * (2 ** pos)
            pos += 1
        return res