Leetcode - Sum of Two Integers

Question

Given two integers a and b, return the sum of the two integers without using the operators + and -.

This is abit_manip question.

Idea

• We want to sum two numbers using bitwise operators
• The AND operator will only set bits that are both set in A and B
• The XOR operator will only set bits in A or B but not both
• When we add two numbers in binary (ex. 1+1 = 0 and 1 + 0 = 1) then we can observe that without carrying bits, A + B is A ^ B. We know when to carry a bit because A & B = 1 and this bit is shifted to the left by 1 place << 1. So the carry bit is (A & B) << 1
• We calculate the sum without carry, then calculate carry setting B to the carry bit until the carry bit is 0
• We also need to apply a mask on B when checking the while condition and when returning A if B > 0 due to python precision handling MASK = 0xFFFFFFFF

Solution