[LeetCode]题解（python）：043-Multiply Strings

Given two numbers represented as strings, return multiplication of the numbers as a string.

Note: The numbers can be arbitrarily large and are non-negative.

Output:the multiply of the two sums

Conditions:数可以无限大，做两个数的乘法

如："23650379502752" 和 "865382861454"

结果："20466633088564555427721408"

注意：

1 最后结果需要将大数的0去掉，同时如果结果为0需要返回串“0”

2 翻转：mul.reverse()

 1 _author_ = "YE"
 2 # -*- coding:utf-8 -*-
 3
 4 class Solution(object):
 5     def multiply(self, num1, num2):
 6         """
 7         :type num1: str
 8         :type num2: str
 9         :rtype: str
10         """
11         len1 = len(num1)
12         len2 = len(num2)
13
14         list1 = [0 for i in range(len1)]
15         list2 = [0 for i in range(len2)]
16
17         for i in range(len1):
18             list1[len1 - 1 - i] = int(num1[i])
19         for i in range(len2):
20             list2[len2 - 1 -i] = int(num2[i])
21
22         # print(list1,list2)
23
24         mul = [0 for i in range(len1 + len2)]
25
26         for i in range(len2):
27             carry = 0
28             for j in range(len1):
29                 mul[i + j] = mul[i + j] + carry + (list2[i] * list1[j]) % 10
30
31                 carry = (list2[i] * list1[j]) // 10
32
33                 if mul[i + j] >= 10:
34                     carry = carry + mul[i + j] // 10
35                     mul[i + j] = mul[i + j] % 10
36
37
38             if carry > 0:
39                 mul[i + len1] += carry
40                 if mul[i + len1] > 10:
41                     mul[i + len1] = mul[i + len1] % 10
42                     carry += mul[i + len1] // 10
43
44         index = len1 + len2 - 1
45         while index >= 0:
46             if mul[index] > 0:
47                 break
48             index -= 1
49
50         if index + 1 < len1 + len2:
51             mul[index+1:] = []
52
53         mul.reverse()
54
55         s = ‘‘
56         for i in range(len(mul)):
57             s += str(mul[i])
58         if s == ‘‘:
59             s = ‘0‘
60         return s
61
62 str1 = ‘12312‘
63 str2 = ‘4234‘
64 s = Solution()
65
66 print(s.multiply(str1,str2))