求4位数组成的最大数和最小数的差

求4位数组成的最大数和最小数的差。将每位数剥离下来放在数组里，对数组排序。然后在把最大数和最小数在循环重组装起来。

#include<stdio.h>
#include<math.h>
int main()
{
	unsigned differFromMaxMin(unsigned num);
	unsigned n;
	scanf("%d", &n);
	differFromMaxMin(n);
	return 0;
}
unsigned differFromMaxMin(unsigned num)
{
	unsigned int arr[4] = { 0 };
	int k = 0;
	while (num>0)
	{
		//计算每一位上的数字
		int i = num % 10;
		arr[k++] = i;
		num = num / 10;
	}
	//每位数字从小到大排序
	for (int i = 0; i < 4; i++)
	{
		for (int j = 0; j < 4 - i; j++)
		{
			if (arr[j] > arr[j + 1])
			{
				int temp = arr[j];
				arr[j] = arr[j + 1];
				arr[j + 1] = temp;
			}

		}
	}
	//最大数字
	unsigned max = 0;
	for (int i = 0; i < 4; i++)
	{
		max = max + arr[i] * pow(10, i);
	}
	//最小数字
	unsigned min = 0;
	for (int i = 3; i >= 0; i--)
	{
		min= min + arr[i] * pow(10, 3-i);
	}
	printf("max is %d\n", max);
	printf("min is %d\n", min);
	printf("max-min is %d\n", max - min);
	return max - min;
}