Multiply Strings(字符串乘法模拟，包含了加法模拟)

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.

要求：字符串表示的数字可能无穷大，并且非负。

class Solution {
private:
    vector<string> tempStrs;
public:
    string add(string num1,string num2)
    {
        int n1=num1.size();
        int n2=num2.size();
        int i=n1-;int j=n2-;
        string resStr;
        int jinwei=;
        while (i>=&&j>=)
        {
            int temp=(num1[i]-'')+(num2[j]-'')+jinwei;
            jinwei=temp>=?:;
            temp%=;
            resStr.push_back(temp+'');
            --i;
            --j;
        }
        if(i>=){
            while (i>=)
            {
                int temp=(num1[i]-'')+jinwei;
                jinwei=temp>=?:;
                temp%=;
                resStr.push_back(temp+'');
                --i;
            }
        }
        else if(j>=){
            while (j>=)
            {
                int temp=(num2[j]-'')+jinwei;
                jinwei=temp>=?:;
                temp%=;
                resStr.push_back(temp+'');
                --j;
            }
        }
        if(jinwei!=){
            resStr.push_back(jinwei+'');
        }
        reverse(resStr.begin(),resStr.end());
        return resStr;
    }
    string multiply(string num1, string num2) {
        if(num1.empty()||num2.empty()) return "";
        if(num1==""||num2=="") return "";
        int jinwei=;
        int n1=num1.size();
        int n2=num2.size();
        if(n2>n1){
            string temp=num1;
            num1=num2;
            num2=temp;
            n1=num1.size();
            n2=num2.size();
        }
        int time=;
        string tempStr;
        string res;
        for(int i=n2-;i>=;--i)
        {
            tempStr.clear();
            jinwei=;
            for(int j=n1-;j>=;--j)
            {
                int temp=(num1[j]-'')*(num2[i]-'')+jinwei;
                jinwei=temp>=?(temp/):;
                temp=temp%;
                tempStr.push_back(temp+'');
            }
            if(jinwei!=){
                tempStr.push_back(jinwei+'');
            }
            reverse(tempStr.begin(),tempStr.end());
            for(int q=;q<time;++q){
                tempStr.push_back('');
            }
            tempStrs.push_back(tempStr);
            ++time;
        }
         if(tempStrs.size()>){
            res=add(tempStrs[],tempStrs[]);
            for (int i=;i<tempStrs.size();++i)
            {
                res=add(res,tempStrs[i]);
            }
            return res;
        }else
        {
            return tempStrs[];
        }

    }
};