leetcode43 string multiplication

class Solution {
    
public:
    string multiply(string num1, string num2) {
    
        vector<int>a,b,c;

        //Put both arrays into the container
        for(int i=0;i<num1.size();i++)
        {
    
            a.push_back(num1[i]-'0');
        }
        
        for(int i=0;i<num2.size();i++)
        {
    
            b.push_back(num2[i]-'0');
        }
        //运算 Because it operates from the ones digit,So turn them upside down
        reverse(a.begin(),a.end());
        reverse(b.begin(),b.end());
        c.resize(a.size()+b.size());//调整c容量

        //运算
        for(int i=0;i<a.size();i++)
        {
    
            for(int j=0;j<b.size();j++)
            {
    
                c[i+j]+=a[i]*b[j];
                c[i+j+1]+=c[i+j]/10;
                c[i+j]=c[i+j]%10;
            }
        }

        //Because it's upside down,So to get the last one is not0的头
        int start=c.size()-1;
        while(start>0&&c[start]==0) start--;//找到头

        //创建string接收
        string ans;
        //将数组转化为字符串
        for(int i=start;i>=0;i--)
        {
    
            ans+='0'+c[i];
        }
        return ans;

    }
};

如有更好想法,欢迎留言！多多指教！