Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -.
Example:
Given a = 1 and b = 2, return 3.
Credits:Special thanks to @fujiaozhu for adding this problem and creating all test cases.
class Solution:
     def getSum(self, a, b):
         max = 0x7FFFFFFF
         mask = 0xFFFFFFFF
         while b != 0:
             a, b = (a ^ b) & mask, ((a & b) << 1) & mask
         return a if a <= max else ~(a ^ mask)
class Solution:
     def getSum(self, a, b):
         max = 0x7FFFFFFF
         mask = 0xFFFFFFFF
         while b != 0:
             a, b = (a ^ b) & mask, ((a & b) << 1) & mask
         return a if a <= max else ~(a ^ mask)