浙大PAT 1069题 1069. The Black Hole of Numbers

#include<stdio.h>#include<stdlib.h>int cmp1(const void* ta,const void* tb){  int* a=(int*)ta;  int* b=(int*)tb;  return *b-*a;}int cmp2(const void* ta,const void* tb){  int* a=(int*)ta;  int* b=(int*)tb;  return *a-*b;}int main(){  int i,j,n;  int last=-1,big,small,ans;  int a[4],b[4];  scanf("%d",&n);  while(1){    for(i=0;i<4;i++){      a[i]=b[i]=n%10;      n=n/10;    }    qsort(a,4,sizeof(int),cmp1);    qsort(b,4,sizeof(int),cmp2);    big=a[0]*1000+a[1]*100+a[2]*10+a[3];    small=b[0]*1000+b[1]*100+b[2]*10+b[3];    ans=big-small;    if(ans==last)       break;    else {      printf("%04d - %04d = %04d\n",big,small,ans);      last=ans;      n=ans;    }  }  return 0;}