LeetCode-in-Java

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

public class Solution {
    public String complexNumberMultiply(String num1, String num2) {
        int countReal;
        int countImagine;
        int[] arr1 = new int[2];
        int[] arr2 = new int[2];

        arr1[0] = Integer.parseInt(num1.substring(0, num1.indexOf("+")));
        arr1[1] = Integer.parseInt(num1.substring(num1.indexOf("+") + 1, num1.length() - 1));

        arr2[0] = Integer.parseInt(num2.substring(0, num2.indexOf("+")));
        arr2[1] = Integer.parseInt(num2.substring(num2.indexOf("+") + 1, num2.length() - 1));

        countReal = arr1[0] * arr2[0] - arr1[1] * arr2[1];
        countImagine = arr1[0] * arr2[1] + arr1[1] * arr2[0];

        return countReal + "+" + countImagine + "i";
    }
}

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