题目

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.

难度

Medium

方法

这题难度虽然标记为Medium，但是比较简单。对于给定字符串a1+b1i和a2+b2i，分别提取出a1,b1,a2,b2,最后的结果为(a1*a2-b1*b2)+(a1*b2+a2*b1)i

python代码

class Solution(object):
    def complexNumberMultiply(self, a, b):
        """
        :type a: str
        :type b: str
        :rtype: str
        """
        a1, b1 = map(int, a[:-1].split("+"))
        a2, b2 = map(int, b[:-1].split("+"))
        return "%s+%si" % (a1*a2-b1*b2, a1*b2+a2*b1)

assert Solution().complexNumberMultiply("1+1i", "1+1i") == "0+2i"
assert Solution().complexNumberMultiply("1+-1i", "1+-1i") == "0+-2i"