1019 数字黑洞

#include
using namespace std;
bool cmp(int a,int b){
	return a>b;
}
int f(vector<int> &a){
	int k1=0;
	vector<int>b(4,0);
	int k2=0;
	for(int i=0;i<4;i++){
		k1=k1*10+a[i];
		b[3-i]=a[i];
		cout<
	}
	cout<<" - ";
	for(int i=0;i<4;i++){
		k2=k2*10+b[i];
		cout<
	}
	k1=k1-k2;
	if(k1<1000&&k1>=100){
		cout<<" = 0"<
	}else if(k1<100&k1>=10){
		cout<<" = 00"<
	}else if(k1<10&&k1>0){
		cout<<" = 000"<
	}else cout<<" = "<
	
	
	a[0]=k1/1000;
	a[1]=(k1/100)%10;
	a[2]=(k1/10)%10;
	a[3]=k1%10;
	sort(a.begin(),a.end(),cmp);
	return k1;
}
int main(){
	int k1;
	cin>>k1;
	vector<int>a(4,0);
	a[0]=k1/1000;
	a[1]=(k1/100)%10;
	a[2]=(k1/10)%10;
	a[3]=k1%10;
	if(a[0]==a[1]&&a[0]==a[2]&&a[0]==a[3]){
		cout<" - "<" = "<<"0000"<
		return 0;
	}
	sort(a.begin(),a.end(),cmp);
	while(f(a)!=6174){
	}
	return 0;
}