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537. Complex Number Multiplication

https://leetcode.com/problems/complex-number-multiplication/description/

Description

Given two strings representing two complex numbers.

You need to return a string representing their multiplication. Note i 2 = -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.

Solution

class Solution:
    def complexNumberMultiply(self, a, b):
        """
        :type a: str
        :type b: str
        :rtype: str
        """
        s1, s2 = a.split('+')
        r1, i1 = int(s1), int(s2[:-1])
        s1, s2 = b.split('+')
        r2, i2 = int(s1), int(s2[:-1])
        return "{}+{}i".format(r1*r2-i1*i2,r1*i2+r2*i1)
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