Lintcode：A + B 问题

给出两个整数a和b, 求他们的和, 但不能使用 + 等数学运算符。

 

a和b都是 32位 整数么？

• 是的

我可以使用位运算符么？

• 当然可以

样例

如果 a=1 并且 b=2，返回3

 

 

 

 

python（原来可以用，现在不能了，应该是数据类型的问题）：

class Solution:
    """
    @param: a: An integer
    @param: b: An integer
    @return: The sum of a and b
    """
    def aplusb(self, a, b):
        # write your code here
        sum = 0 
        carry = 0
        for i in range(32):
            a1 = a & 1
            b1 = b & 1
            val = 0
            if a1== 0 and b1 ==0 and carry ==0:
                val =0
                carry = 0
            elif a1 == 1 and b1 == 1 and carry ==1:
                val =1 
                carry =1
            elif a1 == 0 and b1 ==0 or a1==0 and carry ==0 or b1 ==0 and carry ==0:
                val = 1
                carry = 0
            else:
                val = 0
                carry = 1
            val = val << i
            sum = sum|val
            a = a>>1
            b = b>>1
        return sum

Python(可以用):

class Solution:
    """
    @param a: An integer
    @param b: An integer
    @return: The sum of a and b 
    """
    def aplusb(self, a, b):
        # write your code here
        import ctypes
        a = ctypes.c_int32(a).value
        b = ctypes.c_int32(b).value
        while b != 0:
            carry = ctypes.c_int32(a & b).value
            a = ctypes.c_int32(a ^ b).value
            b = ctypes.c_int32(carry << 1).value
        return a

 

C++：

 

class Solution {
public:
    /*
     * @param : An integer
     * @param : An integer
     * @return: The sum of a and b
     */
    int aplusb(int a, int b) {
        // write your code here
        if(a==0)
            return b;  
        if(b==0)
            return a;  
        int x1 = a ^ b;  
        int x2 = (a & b) << 1;  
        return aplusb(x1, x2);
    }
};