# 1290. Convert Binary Number in a Linked List to Integer

## Description

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.

## Solutions

• /**
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode() {}
*     ListNode(int val) { this.val = val; }
*     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
* }
*/
class Solution {
int ans = 0;
ans = ans << 1 | head.val;
}
return ans;
}
}

• /**
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode() : val(0), next(nullptr) {}
*     ListNode(int x) : val(x), next(nullptr) {}
*     ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution {
public:
int ans = 0;
ans = ans << 1 | head->val;
}
return ans;
}
};

• # Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
def getDecimalValue(self, head: ListNode) -> int:
ans = 0
ans = ans << 1 | head.val
return ans


• /**
* type ListNode struct {
*     Val int
*     Next *ListNode
* }
*/
func getDecimalValue(head *ListNode) (ans int) {
}
return
}

• /**
* class ListNode {
*     val: number
*     next: ListNode | null
*     constructor(val?: number, next?: ListNode | null) {
*         this.val = (val===undefined ? 0 : val)
*         this.next = (next===undefined ? null : next)
*     }
* }
*/

function getDecimalValue(head: ListNode | null): number {
let ans = 0;
ans = (ans << 1) | head.val;
}
return ans;
}


• /**
* function ListNode(val, next) {
*     this.val = (val===undefined ? 0 : val)
*     this.next = (next===undefined ? null : next)
* }
*/
/**
* @return {number}
*/
var getDecimalValue = function (head) {
let ans = 0;
ans = (ans << 1) | head.val;
}
return ans;
};


• /**
* Definition for a singly-linked list.
* class ListNode {
*     public $val = 0; * public$next = null;
*     function __construct($val = 0,$next = null) {
*         $this->val =$val;
*         $this->next =$next;
*     }
* }
*/
class Solution {
/**
* @param ListNode $head * @return Integer */ function getDecimalValue($head) {
$rs = []; while ($head != null) {
array_push($rs,$head->val);
$head =$head->next;
}
$rsStr = implode($rs);
}
}

• // 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
//     }
//   }
// }
impl Solution {
pub fn get_decimal_value(head: Option<Box<ListNode>>) -> i32 {
let mut ans = 0;