Leetcode#43 Multiply Strings

原题地址

想当年初学C++的时候写个大整数加法都快屎了，现在觉得自己还是成长了不少哇。

代码：

string multiply(string num1, string num2) {
        int len1 = num1.length();
        int len2 = num2.length();
        vector<int> buffer(len1 + len2, 0);
        
        for (int i = len1 - 1; i >= 0; i--)
            for (int j = len2 - 1; j >= 0; j--)
                buffer[len1 - 1 - i + len2 - 1 - j] += (num1[i] - '0') * (num2[j] - '0');
        
        for (int i = 0, carry = 0; i < len1 + len2; i++) {
            buffer[i] += carry;
            carry = buffer[i] / 10;
            buffer[i] %= 10;
        }
        
        string res;
        int p = len1 + len2 - 1;
        while (p >= 0 && buffer[p] == 0) p--;
        while (p >= 0) {
            res += buffer[p] + '0';
            p--;
        }
        
        return res.empty() ? "0" : res;
    }