1. What I learned

    a. class LinkedList

        ‘self.head’ in ‘def init(self)’ of class ‘LinkedList’ refers to the head node.

    b. int(num1,num2) method

        It converts ‘num1’ in given based(‘num2’).
        ex) int(101,2) –> 5

2. How I sloved

    I sent a linked list to Class ‘solution’. I add the node’s value to ‘num’ and moved to the next node. I kept doing this for all the nodes, and I returned the result.

3. Code

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

4. Result

        Runtime : 20 ms(97.70%), Memory usage : 13.9 MB(100.00%)
        (Runtime can be different by a system even if it is a same code.)

Check out the my GitHub repo for more info on the code. If you have questions, you can leave a reply on this post.