LeetCode461：Hamming Distance

The Hamming distance between two integers is the number of positions at which the corresponding bits are different.

Given two integers x and y, calculate the Hamming distance.

Note:
0 ≤ x, y < 231.

Example:

Input: x = 1, y = 4

Output: 2

Explanation:
1   (0 0 0 1)
4   (0 1 0 0)
       ↑   ↑

The above arrows point to positions where the corresponding bits are different.

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LeetCode：链接

汉明距离，即两个数的二进制表示中对应位上数字（0／1）不相同的个数。很容易想到这题应该用异或。接下来的问题就转换成数异或的结果中1的个数。

怎么数1的个数？这里有个简单的方法：

num = 0b00110
count = 0
while num:
    num &= num - 1
    count += 1
print(count)

每次num &= num - 1，num二进制值的最低位1都会变成0，即每次去掉一个1，直到其值为0。

class Solution(object):
    def hammingDistance(self, x, y):
        """
        :type x: int
        :type y: int
        :rtype: int
        """
        xor = x ^ y
        count = 0
        while xor:
            xor &= xor - 1
            count += 1
        return count