1411 Convert Binary Number In A Linked List To Integer

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.

The most significant bit is at the head of 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

 

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 struct ListNode {
//   pub val: i32,
//   pub next: Option<Box<ListNode>>
// }
// 
// impl ListNode {
//   #[inline]
//   fn new(val: i32) -> Self {
//     ListNode {
//       next: None,
//       val
//     }
//   }
// }
use std::ptr::null;
impl Solution {
    pub fn get_decimal_value(mut head: Option<Box<ListNode>>) -> i32 {
        let mut res = 0;
        while let Some(node) = head {
            res = (res << 1) | node.val;
            head = node.next;
        }
        res

    }
}