Problem

Calculate the sum of two integersaandb, but you arenot allowedto use the operator+and-.

Example:
Givena= 1 andb= 2, return 3.

思路

• Sum of two bits can be obtained by performing XOR (^) of the two bits.
• Carry bit can be obtained by performing AND (&) of two bits.
• keep adding until no carry

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