Given two strings representing two .

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.

public class Solution {    public String complexNumberMultiply(String a, String b) {        if (a == null || b == null)            return null;                String[] ap = a.split("\\+");        int p1 = Integer.parseInt(ap[0]);        int k1 = Integer.parseInt(ap[1].substring(0, ap[1].length()-1));                String[] bp = b.split("\\+");        int p2 = Integer.parseInt(bp[0]);        int k2 = Integer.parseInt(bp[1].substring(0, bp[1].length()-1));                int r1 = p1*p2;        int ri = p1*k2 + k1*p2;        int ri2 = -(k1*k2);                int p3 = r1 + ri2;        int k3 = ri;                return p3+"+"+k3+"i";            }}