Complex Number Multiplication

比较考验精细处理的问题，注意加减符号问题就可以了

class Solution(object):
    def complexNumberMultiply(self, a, b):
        """
        :type a: str
        :type b: str
        :rtype: str
        """
        realA, virA = a.split('+')
        realB, virB = b.split('+')
        realA = int(realA) if realA[0] != '-' else -int(realA[1:])
        realB = int(realB) if realB[0] != '-' else -int(realB[1:])
        virA = int(virA[:-1]) if virA[0] != '-' else -int(virA[1:-1])
        virB = int(virB[:-1]) if virB[0] != '-' else -int(virB[1:-1])

        return `realA * realB + (-virA * virB)` + '+' + `virA * realB + virB * realA` + 'i'