ConvertBinaryNumberInALinkedListToInteger.js

// Source : https://leetcode.com/problems/convert-binary-number-in-a-linked-list-to-integer
// Author : Dean Shi
// Date   : 2021-12-14

/***************************************************************************************
 * 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.
 * 
 ***************************************************************************************/

/**
 * 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 = head.val

    while (head = head.next) {
        result = result * 2 + head.val
    }
    return result
};