解法一

注意substring和indexOf等方法的使用。

  1. class Solution {
  2.     public String complexNumberMultiply(String a, String b) {
  3.         ComplexNumber c1 = new ComplexNumber(a);
  4.         ComplexNumber c2 = new ComplexNumber(b);
  5.         return c1.multiply(c2).toString();
  6.     }
  7. }
  9. class ComplexNumber {
  10.     public Integer realPart;
  11.     public Integer imaginaryPart;
  13.     public ComplexNumber(Integer realPart, Integer imaginaryPart) {
  14.         this.realPart = realPart;
  15.         this.imaginaryPart = imaginaryPart;
  16.     }
  18.     public ComplexNumber(String s) {
  19.         int pos1 = s.indexOf('+');
  20.         int pos2 = s.indexOf('i');
  21.         realPart = Integer.parseInt(s.substring(0, pos1));
  22.         imaginaryPart = Integer.parseInt(s.substring(pos1 + 1, pos2));
  23.     }
  25.     public ComplexNumber multiply(ComplexNumber c) {
  26.         return new ComplexNumber(
  27.                 realPart * c.realPart - imaginaryPart * c.imaginaryPart,
  28.                 realPart * c.imaginaryPart + imaginaryPart * c.realPart);
  29.     }
  31.     @Override
  32.     public String toString() {
  33.         return realPart.toString() + "+" + imaginaryPart.toString() + "i";
  34.     }
  35. }