# 判断n是否为奇数
if n & 1:
    print("奇数")
else:
    print("偶数")

a = a ^ b
b = a ^ b
a = a ^ b

# 判断n的第k位（从0开始）是否为1
if n & (1 << k):
    print("第k位是1")

n = n | (1 << k)

n = n & ~(1 << k)

n = n ^ (1 << k)

lowbit = n & (-n)

n = n & (n - 1)

# 2的幂次只有一个1
if n > 0 and (n & (n - 1)) == 0:
    print("是2的幂次")

def count_ones(n):
    count = 0
    while n:
        n = n & (n - 1)
        count += 1
    return count

class Solution:
    def singleNumber(self, nums: List[int]) -> int:
        result = 0
        for num in nums:
            result ^= num
        return result

class Solution:
    def hammingWeight(self, n: int) -> int:
        count = 0
        while n:
            n &= n - 1
            count += 1
        return count

class Solution:
    def isPowerOfTwo(self, n: int) -> bool:
        return n > 0 and (n & (n - 1)) == 0

class Solution:
    def countBits(self, n: int) -> List[int]:
        # dp[i] = dp[i & (i-1)] + 1
        result = [0] * (n + 1)
        for i in range(1, n + 1):
            result[i] = result[i & (i - 1)] + 1
        return result