537 - Complex Number Multiplication\.

Medium

A complex number can be represented as a string on the form <code>"real+imaginaryi"</code> 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].

• <code>i² == -1</code>.

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 + i2 + 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 + i2 - 2 \* i = -2i, and you need convert it to the form of 0+-2i.

Constraints:

• num1 and num2 are valid complex numbers.