537. Complex Number Multiplication（python+cpp）

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题目：

Given two strings representing two complex numbers.
You need to return a string representing their multiplication. Note i²= -1 according to the definition.
Example 1:

Input: "1+1i", "1+1i" 
Output: "0+2i" 
Explanation: (1 + i) *(1 + i) = 1 + i2 + 2 * i = 2i, and you need convert it to the form of 0+2i. 

Example 2:

Input: "1+-1i", "1+-1i" 
Output: "0+-2i" 
Explanation:(1 - i) * (1 - i) = 1 + i2 - 2 * i = -2i, and you need convert it to the form of 0+-2i. 

Note:
The input strings will not have extra blank.
The input strings will be given in the form of a+bi, where the integer a and b will both belong to the range of [-100, 100]. And the output should be also in this form.

解释：
实现复数乘法。明白了复数的乘法的计算过程后，其实就是字符串解析问题了。
python代码：

class Solution(object):
    def complexNumberMultiply(self, a, b):
        """
        :type a: str
        :type b: str
        :rtype: str
        """
        a1,a2=map(int,a[:-1].split('+'))
        b1,b2=map(int,b[:-1].split('+'))
        return '%d+%di'%(a1*b1-a2*b2,a2*b1+b2*a1)

c++代码：

#include<sstream>
#include<cstdlib>
using namespace std;
class Solution {
public:
    string complexNumberMultiply(string a, string b) {
        a=a.substr(0,a.size()-1);
        b=b.substr(0,b.size()-1);
        istringstream aa(a);
        istringstream bb(b);
        vector<int> a_list;
        vector<int> b_list;
        string word;
        while(getline(aa,word,'+'))
        {
            a_list.push_back(atoi(word.c_str()));
        }
        while(getline(bb,word,'+'))
        {
            b_list.push_back(atoi(word.c_str()));
        }
        int res_n=a_list[0]*b_list[0]-a_list[1]*b_list[1];
        int res_i=a_list[0]*b_list[1]+a_list[1]*b_list[0];
        return to_string(res_n)+"+"+to_string(res_i)+"i";
    }
};

总结：