Complex Number Multiplication

题目来源
求字符串复数的乘法操作。主要是考虑string的一些操作，我想了想，先找出“+”在哪里，然后分割实部和虚部，然后进行计算，用了stringstream。代码如下：

class Solution {
public:
    string complexNumberMultiply(string a, string b) {
        int n1 = a.size(), n2 = b.size();
        string realA, realB, imageA, imageB;
        for (int i=0; i<n1; i++) {
            if (a[i] == '+') {
                realA = a.substr(0, i);
                imageA = a.substr(i+1, n1-i-2);
            }
        }
        for (int i=0; i<n2; i++) {
            if (b[i] == '+') {
                realB = b.substr(0, i);
                imageB = b.substr(i+1, n2-i-2);
            }
        }
        int irealA, irealB, iimageA, iimageB;
        istringstream (realA) >> irealA;
        istringstream (realB) >> irealB;
        istringstream (imageA) >> iimageA;
        istringstream (imageB) >> iimageB;
        return to_string(irealA * irealB - iimageA * iimageB) + "+" + to_string(irealA * iimageB + irealB * iimageA) + "i";
    }
};

然后发现自己还是太弱了，streamstring不会用。
看了下讨论区，代码如下：

class Solution {
public:
    string complexNumberMultiply(string a, string b) {
        int ra, ia, rb, ib;
        char buff;
        stringstream aa(a), bb(b), ans;
        aa >> ra >> buff >> ia >> buff;
        bb >> rb >> buff >> ib >> buff;
        ans << ra*rb - ia*ib << "+" << ra*ib + rb*ia << "i";
        return ans.str();
    }
};