/*
 * @lc app=leetcode id=1290 lang=rust
 *
 * [1290] Convert Binary Number in a Linked List to Integer
 *
 * https://leetcode.com/problems/convert-binary-number-in-a-linked-list-to-integer/description/
 *
 * algorithms
 * Easy (79.99%)
 * Total Accepted:    32.5K
 * Total Submissions: 40.7K
 * Testcase Example:  '[1,0,1]'
 *
 * 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.
// #[derive(PartialEq, Eq, Clone, Debug)]
// // pub structListNode {
//   pub val: i32,
//   pub next: Option<Box<ListNode>>
// }

// impl ListNode {
//   #[inline]
//   fn new(val: i32) -> Self {
//     ListNode {
//       next: None,
//       val
//     }
//   }
// }

impl Solution {
    pub fn get_decimal_value(head: Option<Box<ListNode>>) -> i32 {
        let mut res = 0; 
        let mut it = head;
        while let Some(node) = it {
            res = res << 1 | node.val; 
            it = node.next;
        }
        res 
    }
}
// pub structSolution;