A1069 . The Black Hole of Numbers (20)

#include<cstdio>
#include<cstring>
#include<algorithm>
//仔细观察，合并
using namespace std;

bool cmp(char c1,char c2){
return c1 > c2;
}
int main(){
int n,n1,n2;
char str[5];
scanf("%d",&n);
while(1){
sprintf(str,"%04d",n);
int len = strlen(str);
sort(str,str+len);
sscanf(str,"%d",&n1);
sort(str,str+len,cmp);
sscanf(str,"%d",&n2);
n = n2 - n1;
printf("%04d - %04d = %04d\n",n2,n1,n);
if(n==0 || n == 6174) break;
}
return 0;
}