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:
The input strings will not have extra blank.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.关键是提取出系数，使用了split
public class Solution { public String complexNumberMultiply(String a, String b) { int p1 = Integer.valueOf(a.split("\\+")[0]); int p2 = Integer.valueOf(a.split("\\+")[1].split("[i]")[0]); int p3 = Integer.valueOf(b.split("\\+")[0]); int p4 = Integer.valueOf(b.split("\\+")[1].split("[i]")[0]); return ""+(p1*p3-p2*p4)+"+"+(p1*p4+p2*p3)+"i"; } } 他人用Stream的写法 public String complexNumberMultiply(String a, String b) { int[] coefs1 = Stream.of(a.split("\\+|i")).mapToInt(Integer::parseInt).toArray(), coefs2 = Stream.of(b.split("\\+|i")).mapToInt(Integer::parseInt).toArray(); return (coefs1[0]*coefs2[0] - coefs1[1]*coefs2[1]) + "+" + (coefs1[0]*coefs2[1] + coefs1[1]*coefs2[0]) + "i"; }