1019. 数字黑洞 (20)

#include<stdio.h>

void swap1(int *a, int *b)
{
int temp;
temp = *a;
*a = *b;
*b = temp;
}

int x=0,big=0,small=0,a[4],s;

void fun(int x)
{
int i,j;
a[0] = x%10;
a[1] = x%100/10;
a[2] = x%1000/100;
a[3] = x/1000;
for(i=0; i<3; i++)
for(j=0; j<3-i; j++)
if(a[j]>a[j+1])
swap1(&a[j],&a[j+1]);
big = a[0] + a[1]*10 + a[2]*100 + a[3]*1000;
small = a[3] + a[2]*10 + a[1]*100 + a[0]*1000;
}
int main()
{
scanf("%d",&x);

while(s!=6174)
{
fun(x);
s = big - small;
printf("%04d - %04d = %04d\n",big,small,s);
if(s==0)
break;
x = s;
}
return 0;
}