A + B Problem

Write a function that add two numbers A and B. You should not use + or any arithmetic operators.

分析：

典型的Bit Operation.

class Solution {
    /*
     * param a: The first integer
     * param b: The second integer
     * return: The sum of a and b
     */
    public int aplusb(int a, int b) {
        if (a == 0) return b;
        int sum = a ^ b;
        int carry = (a & b) << 1;
        return aplusb(carry, sum);
    }
};