不用加减实现加法

class Solution{
public:
	int aPlusb(int a, int b){
		int result = a ^ b;
		int carry = (a & b) <<1
		if(carry)
			result = aPlusb(result, carry);
		
		return result;
	}
	
	int aPlusb(int a, int b){
		int ansRes = 0;
		while(b != 0){
			ansRes = a & b;
			a = a^b;
			b = ansRes<<1;
		}
        return ansRes;
	}
};