#include<stdio.h>
#include<stdlib.h>

void select_sort(int data[], int len)
{
	for (int i = 0; i < len; i++)
	{
		for (int j = i + 1; j < len; j++)
		{
			if (data[i] > data[j])
			{
			    int temp = data[i];
				data[i]=data[j];
				data[j]= temp;
			}
		}
	}
}
int kaprekar(int num)
{
	while (num != 6174)
	{
		int bits[4] = { 0 };
		int max_num = 0,min_num=0;
		int k = 1000; 
		for (int i = 0; i < 4; i++)//获取4个位
		{
			bits[i] = num / k;
			num %= k;
			k /= 10;
		}
		select_sort(bits, 4);
		for (int i = 0; i < 4; i++)
		{
			max_num = max_num * 10 + bits[4 - i - 1];
			min_num = min_num * 10 + bits[i];
		}
		num = max_num - min_num;
	}
	return 1;
}

int main()
{
	for (int i = 1000; i < 9999; i++)
	{
		kaprekar(i);
	}
	system("pause");
	return 0;
}