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.

int getSum(int a, int b) {    int ans;    while(b)    {        ans = a^b;        b = (a&b)<<1;        a = ans;    }    return ans;}

参考：

http://blog.csdn.net/hackbuteer1/article/details/7390093

位运算实现加法运算