思路:
按照数学公式进行拆分和计算.
class Solution {
public String complexNumberMultiply(String a, String b) {
String[] a_arr=a.split("\\+");
String[] b_arr=b.split("\\+");
int a1=Integer.parseInt(a_arr[0]);
int a2=Integer.parseInt(a_arr[1].replace("i",""));
int b1=Integer.parseInt(b_arr[0]);
int b2=Integer.parseInt(b_arr[1].replace("i",""));
String res1=""+(a1*b1+a2*b2*(-1));
String res2=""+(a1*b2+a2*b1);
return res1+"+"+res2+"i";
}
}