leetcode 1290. Convert Binary Number in a Linked List to Integer（python）

描述

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

Note:

The Linked List is not empty.
Number of nodes will not exceed 30.
Each node's value is either 0 or 1.

解析

根据题意，其实就是求链表组成的字符串表示的二进制数转化为十进制的值，就是一个简单的二进制转十进制问题，直接按照链表的顺序从前到后进行计算即可，当前节点所对应的十进制数为之前的 res * 2 + 当前的节点的值，遍历结束得到的 res 即可结果。

解答

class Solution(object):
    def getDecimalValue(self, head):
        """
        :type head: ListNode
        :rtype: int
        """
        res = head.val
        while head.next:
            res = res * 2 + head.next.val
            head = head.next
        return res

运行结果

Runtime: 16 ms, faster than 81.12% of Python online submissions for Convert Binary Number in a Linked List to Integer.
Memory Usage: 13.5 MB, less than 15.05% of Python online submissions for Convert Binary Number in a Linked List to Integer.

原题链接：https://leetcode.com/problems/convert-binary-number-in-a-linked-list-to-integer/

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