LeetCode in Kotlin

537. Complex Number Multiplication

Medium

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.

Solution

class Solution {
    fun complexNumberMultiply(num1: String, num2: String): String {
        val countReal: Int
        val countImagine: Int
        val arr1 = IntArray(2)
        val arr2 = IntArray(2)
        arr1[0] = num1.substring(0, num1.indexOf("+")).toInt()
        arr1[1] = num1.substring(num1.indexOf("+") + 1, num1.length - 1).toInt()
        arr2[0] = num2.substring(0, num2.indexOf("+")).toInt()
        arr2[1] = num2.substring(num2.indexOf("+") + 1, num2.length - 1).toInt()
        countReal = arr1[0] * arr2[0] - arr1[1] * arr2[1]
        countImagine = arr1[0] * arr2[1] + arr1[1] * arr2[0]
        return countReal.toString() + "+" + countImagine + "i"
    }
}

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