[leetcode]371. Sum of Two Integers

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

分析：

求两数之和，且不能用+，-。可以用用异或算不带进位的和，用与并左移1位来算进位，然后把两者加起来即可。

class Solution {
public:
    int getSum(int a, int b) {
        if(b == 0)
            return a;
        int sum = a ^ b;
        int carry = (a & b) << 1;
        return getSum(sum , carry);
    }
};