https://leetcode.com/problems/convert-binary-number-in-a-linked-list-to-integer/description/

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.

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

Constraints:

The Linked List is not empty. Number of nodes will not exceed 30. Each node's value is either 0 or 1.