LeetCode 1290. Convert Binary Number in a Linked List to Integer 将链表中二进制转换为整数

难度： 简单

题目：

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.

示例1：
在这里插入图片描述

Input: head = [1,0,1]
Output: 5
Explanation: (101) in base 2 = (5) in base 10

示例2：

Input: head = [0]
Output: 0

示例3：

Input: head = [1]
Output: 1

示例4：

Input: head = [1,0,0,1,0,0,1,1,1,0,0,0,0,0,0]
Output: 18880

示例5：

Input: head = [0,0]
Output: 0

限制：

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

思路：
这道题目的是将链表中每个结点的值先转化为二进制的形式，然后将其转化为十进制

比较简单的做法（耗费了额外空间）：

链表 -> 数组
整型数组 - > 字符型数组
字符型数组 - > 二进制字符串
二进制字符串 - > 十进制数

代码：

# 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:
        arr, str_arr = [], ""
        while head:  # linked list to array
            arr.append(head.val)
            head = head.next
        arr = list(map(str, arr))  # list of int -> list of str
        str_arr = "".join(arr)  # list of str -> str
        return int(str_arr, 2)  # str -> int

测试结果：

Accepted!

Runtime: 24 ms, faster than 88.53% of Python3 online submissions for Convert Binary Number in a Linked List to Integer.

Memory Usage: 12.7 MB, less than 100.00% of Python3 online submissions for Convert Binary Number in a Linked List to Integer.

复杂度分析：

Time Complexity: O(n)

Space Complexity: O(n)

来源：CSDN

作者：ceezyyy11

链接：https://blog.csdn.net/ceezyyy11/article/details/103906842

标签

convert