LeetCode_Multiply Strings

Posted on | In | Views:

Multiply Strings

Given two non-negative integers num1 and num2 represented as strings, return the product of num1 and num2, also represented as a string.
（用非库函数的方式返回两个字符串表示的整数的乘积）

Example:



Note:

  • The length of both num1 and num2 is < 110.
  • Both num1 and num2 contain only digits 0-9.
  • Both num1 and num2 do not contain any leading zero, except the number 0 itself.
  • You must not use any built-in BigInteger library or convert the inputs to integer directly.

实现库函数 atoi 和 itoa

由于题中备注了不让使用自带的库函数，因此可以自己实现。其中在 python 中 ord()表示将字符转换为ASCII码，chr()表示将ASCII码转换为字符。具体实现过程如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
class Solution:
    def multiply(self, num1, num2):
        """
        :type num1: str
        :type num2: str
        :rtype: str
        """
        def atoi(s):
            result = 0
            for char in s:
                result = result * 10 + (ord(char) - ord('0'))
            return result
    
        def itoa(num):
            if num == 0:
                return "0"
            s = ""
            while num:
                char = num % 10 + ord('0')
                s = chr(char) + s
                num = num // 10
            
            return s
        
        return itoa(atoi(num1) * atoi(num2))