LeetCode:Complex Number Multiplication

537. Complex Number Multiplication

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.

思路：思路比较直接，关键在于找到各个方程式的系数就可以了。

int getpos(string s,char c)
{
    int len = s.length();
    int i = 0;
    for (; i < len; i++)
    {
        if (s[i] == c)
            return i;
    }
}
int geta(string s)
{
    return stoi(s.substr(0, getpos(s, '+') + 1).c_str());
}
int getb(string s)
{
    return stoi(s.substr(getpos(s, '+') + 1,s.length()-getpos(s,'+')-1).c_str());
}
string complexNumberMultiply(string a, string b) {
    
    ostringstream s1,s2;
    s1 << geta(a)*geta(b) - getb(a)*getb(b);
    s2 << geta(a)*getb(b) + getb(a)*geta(b);
    return s1.str()+"+"+s2.str()+"i";
}

如果你有任何疑问或新的想法，欢迎在下方评论。