LeetCode-Multiply Strings

现附上代码：

class Solution {
public:
    string multiply(string num1, string num2) {
        if (num1 == "0" || num2 == "0")return "0";
        vector res (num1.size()+num2.size()-1,0);
        int len = num1.size()+num2.size()-2;
        string ans = "";
        for (int i=0;i 0){
            digit = overflow%10;
            overflow = overflow/10;
            ans.append(1,digit+'0');
        }
        reverse(ans.begin(),ans.end());
        res.clear();
        vector().swap(res);
        return ans;
    }
};