LeetCode 371 : Sum of Two Integers(Java)

题目：

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.

解题思路：用异或算不带进位的和，用与并左移一位来算进位，再把两者相加即可，直到进位为全0。递归的解法如下：

public 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);
}
}