371. Sum of Two Integers.cpp

/*

Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -.

Example 1:

Input: a = 1, b = 2
Output: 3
Example 2:

Input: a = -2, b = 3
Output: 1


Using ^ and & to calculate
*/
class Solution {
public:
    int getSum(int a, int b) {
        if (b == 0) return a;
        int sum = a ^ b;
        int carry = (a & b & 0x7fffffff) << 1;
        return getSum(sum, carry);
    }
};