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## Problem

A complex number can be represented as a string on the form “real+imaginaryi” where:

• real is the real part and is an integer in the range [-100, 100].
• imaginary is the imaginary part and is an integer in the range [-100, 100].
• i^2 == -1.

Given two complex numbers num1 and num2 as strings, return a string of the complex number that represents their multiplications.

Example 1:

Input: num1 = "1+1i", num2 = "1+1i"
Output: "0+2i"
Explanation: (1 + i) * (1 + i) = 1 + i^2 + 2 * i = 2i, and you need convert it to the form of 0+2i.


Example 2:

Input: num1 = "1+-1i", num2 = "1+-1i"
Output: "0+-2i"
Explanation: (1 - i) * (1 - i) = 1 + i^2 - 2 * i = -2i, and you need convert it to the form of 0+-2i.


Constraints:

• num1 and num2 are valid complex numbers.

## Code

class Solution {
public String complexNumberMultiply(String a, String b) {
String x[] = a.split("\\+");
String y[] = b.split("\\+");

int aReal = Integer.parseInt(x);
int aImg = Integer.parseInt(x.replace("i",""));
int bReal = Integer.parseInt(y);
int bImg = Integer.parseInt(y.replace("i",""));

return (aReal * bReal - aImg * bImg) + "+" + (aReal * bImg + aImg * bReal) + "i";
}
}