[题]写一个函数返回参数二进制中1的个数。

1.

int main()
{
	int num = 0;
	int count = 0;
	scanf("%d", &num);
	while (num)
	{
		if (num % 2 == 1)
		{
			count++;
		}
		num /= 2;
	}
	printf("%d\n", count);
	return 0;
}

2.

int main()
{
	int num = 0;
	scanf("%d", &num);
	int i = 0;
	int count = 0;
	for (i = 0; i <=32;i++)
	{
		if ((num >> i) & 1 == 1)
			count++;
	}
	printf("%d\n", count);
	return 0;
}

3.

int main()
{
	int n = 0;
	scanf("%d", &n);
	int count = 0;
	while (n)
	{
		if (n)
		{
			count++;
		}
		n = n & (n - 1);
	}
	printf("%d\n", count);
	return 0;
}