LeetCode 1290. Convert Binary Number in a Linked List to Integer

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:

1290ex1 
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.

 

 

Solution

Python

# 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:
        binary_nums = []
        while head != None:
            binary_nums.append(str(head.val))
            head = head.next
        
        bin_num = "".join(binary_nums)
        return int(bin_num, 2)

Java