0537. Complex Number Multiplication

https://leetcode.com/problems/complex-number-multiplication

Description

A complex number can be represented as a string on the form "**real**+**imaginary**i" 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].

• i2 == -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 + 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.

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