1290. Convert Binary Number in a Linked List to Integer

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

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {number}
 */
var getDecimalValue = function(head) {
    let result = 0
    while(head != null) {
        result = result*2 + head.val
        head = head.next
    }
    
    return result
}

var getDecimalValue = function(head) {
    let s = ""; 
    while (head !== null) {
        s += head.val.toString(); 
        head = head.next; 
    }
    return parseInt(s, 2); 
};

Note

parseInt
parseInt(string, radix);