Convert Binary Number in a Linked List to Integer In Java

Convert Binary Number in a Linked List to Integer In Java

Objective:

You are given the head of a singly linked list.
Each node in the list stores a binary digit: either 0 or 1.

This linked list represents a binary number, where the most significant bit (MSB) is at the start (head) of the list, and the least significant bit (LSB) is at the end.

Your task is to:
👉 Convert this binary number into its decimal (base-10) equivalent
👉 And return that integer value

Solution:

class Solution {
    public int getDecimalValue(ListNode head) {
        int result =0;
        while(head!=null) {
            result = result*2+head.val;
            head = head.next;
        }
        return result;
    }
}

Explanation:

1. Starts with result=0;
2. Traverse the list
   1. Multiply current ‘result’ by 2 (left shift)
   2. Add the curent node’s value (0 or 1)
3. It mimics converting binary to decimal by shifting and adding bits

For Ex:

Linked List: 1 -> 0 -> 1
Step By Step:

result = 0
result = 0*2+1 =1
result = 1*2+0 = 2
result = 2*2+1 = 5

So the final result is: 5