537. Complex Number Multiplication

#### QUESTION:

Given two strings representing two complex numbers.

You need to return a string representing their multiplication. Note i2 = -1 according to the definition.

Example 1:

``````Input: "1+1i", "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: "1+-1i", "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.

``````

Note:

1. The input strings will not have extra blank.
2. The input strings will be given in the form of a+bi, where the integer a and b will both belong to the range of [-100, 100]. And the output should be also in this form.

#### SOLUTION:

``````public class Solution {
public String complexNumberMultiply(String a, String b) {
String[] result = a.split("\\+");
int m = Integer.parseInt(result);
int n = Integer.parseInt(result.split("i"));
result = b.split("\\+");
int x = Integer.parseInt(result);
int y = Integer.parseInt(result.split("i"));
int i = m*x + n*y*(-1);
int j = m*y + n*x;
return i+"+"+j+"i";
}
}
``````
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