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.
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
Example 3:
Input: head = [1] Output: 1
Example 4:
Input: head = [1,0,0,1,0,0,1,1,1,0,0,0,0,0,0] Output: 18880
Example 5:
Input: head = [0,0] Output: 0
Constraints:
<li>The Linked List is not empty.</li>
<li>Number of nodes will not exceed <code>30</code>.</li>
<li>Each node's value is either <code>0</code> or <code>1</code>.</li>