## Question

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:5Explanation:(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`

.

## Python Solution

# Definition for singly-linked list. # class ListNode: # def __init__(self, val=0, next=None): # self.val = val # self.next = next class Solution: def getDecimalValue(self, head: ListNode) -> int: res='' while head.next!=None: res+=str(head.val) head=head.next res+=str(head.val) res=res[::-1] s=0 for i in range(len(res)): s+=int(res[i])*(2**i) return s