Leetcode之Multiply Strings

      字符串相乘，题目如下：

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.

    根据上面的字符串的相乘，变成数组相乘。

 C++ Code 

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
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50

class Solution
{
public:
    string multiply(string s1, string s2)
    {
        if(s1 == "0" || s2 == "0") return "0";
        int len1 = s1.length();
        int len2 = s2.length();
        int len3 = len1 + len2;


        vector<int> num1(len1, 0);
        vector<int> num2(len2, 0);
        vector<int> num3(len1 + len2, 0);
        for(int i = 0; i < len1; i++)
        {
            num1[i] = s1[i] - '0';
        }
        for(int i = 0; i < len2; i++)
        {
            num2[i] = s2[i] - '0';
        }


        for(int i = 0; i < len1; i++)
        {
            for(int j = 0; j < len2; j++)
            {
                num3[i + j + 1] += num1[i] * num2[j];
            }
        }
        string ss = "";
        for(int i = len3 - 1; i >= 0; i--)
        {
            if(i > 0)
            {
                num3[i - 1] += num3[i] / 10;
            }
            num3[i] = num3[i] % 10;
            ss = char(num3[i] + '0') + ss;
        }
        ss = ss[0] == '0' ? ss.substr(1) : ss;

        return ss;
    }
};