1290. Convert Binary Number in a Linked List to Integer

Difficulty: Easy

Related Topics: Linked List, Bit Manipulation

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:

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

Solution

Language: Java

class Solution {

    public int getDecimalValue(ListNode head) {
        int num = 0;
        while (head != null) {
            // 这条语句相当于
            // num = num * 2 + head.val
            num = (num << 1) | head.val;
            head = head.next;
        }
        return num;
    }

}