README_EN.md

1290. Convert Binary Number in a Linked List to Integer

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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

Python3

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None


class Solution:
    def getDecimalValue(self, head: ListNode) -> int:
        res = 0
        while head:
            res = (res << 1) + head.val
            head = head.next
        return res

Java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public int getDecimalValue(ListNode head) {
        int res = 0;
        while (head != null) {
            res = (res << 1) + head.val;
            head = head.next;
        }
        return res;
    }
}

C++

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    int getDecimalValue(ListNode* head) {
        int res = 0;
        while (head != NULL) {
            res = (res << 1) + head->val;
            head = head->next;
        }
        return res;
    }
};

JavaScript

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} head
 * @return {number}
 */
var getDecimalValue = function (head) {
    let res = 0;
    while (head != null) {
        res = (res << 1) + head.val;
        head = head.next;
    }
    return res;
};

TypeScript

/**
 * Definition for singly-linked list.
 * 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;
    let cur = head;
    while (cur) {
        ans = (ans << 1) | cur.val;
        cur = cur.next;
    }
    return ans;
}

Rust

// 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;
        let mut cur = &head;
        while let Some(node) = cur {
            ans = (ans << 1) | node.val;
            cur = &node.next;
        }
        ans
    }
}

C

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */


int getDecimalValue(struct ListNode *head) {
    int ans = 0;
    struct ListNode *cur = head;
    while (cur) {
        ans = (ans << 1) | cur->val;
        cur = cur->next;
    }
    return ans;
}

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