[LeetCode] Sum of Two Integers

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.

不用'+'和'-'实现两个整数相加，使用XOR计算各个位上不进位相加的结果，使用&计算各个位上的进位情况，使进位在每一步运算后左移1位。循环每一步直到进位为0。

class Solution {
public:
    int getSum(int a, int b) {
        int res = 0, carry = INT_MAX;
        while (carry) {
            res = a ^ b;
            carry = a & b;
            carry <<= 1;
            a = res;
            b = carry;
        }
        return res;
    }
};
// 3 ms