Sum—LeetCode-371 Sum of Two Integers

题目描述：

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.

思想：（1）两个数异或，相当于两个数的二进制不带进位相加

          （2）两个数相与，相当于得到要进位的数字

          （3）循环相加，直到没有进位

public int getSum(int a, int b) {
        int tempSum = 0;
        do{
            tempSum = a ^ b;
            int c = (a & b) << 1;
            a = tempSum;
            b = c;
        } while(b != 0);
        return a;
    }