PAT (Basic Level) Practice （中文）--1019 数字黑洞 (20 分)

#include<bits/stdc++.h>

using namespace std;
int ans;
int res;
int last;
int cmpp(char a,char b){
	return a > b;
}

int max_trans(string ss){
    ans = 0;
	sort(ss.begin(),ss.end(),cmpp);
//	cout<<"max__"<<ss<<endl;
	for(int i=0;i<ss.size();i++){
		ans += (ss[i]-'0');
		ans *= 10;
	}
	return ans/10;
}

int min_trans(string ss){
	ans = 0;
	sort(ss.begin(),ss.end());
	for(int i=0;i<ss.size();i++){
		ans += (ss[i]-'0');
		ans *= 10;
	}
	return ans/10;
}

bool check(string ss){
	 int l = ss.size();
	 for(int i=1;i<l;i++){
	 	if(ss[i]!=ss[i-1]){
	 	   return false;
		}
	 }
	 return true;
}

string too_string(int n){
	   int pos = n;
	   string s1;
	   while(pos!=0){
	   	res = pos % 10;
	   	pos /=10;
	   	s1 += (res + '0');
	   }
	   reverse(s1.begin(),s1.end());
	   return s1;
}

int main(){
	string s;
	cin>>s;
	if(check(s)){
		cout<<setw(4)<<setfill('0')<<s;
		cout<<" - ";
		cout<<setw(4)<<setfill('0')<<s;
		cout<<" = "<<"0000"<<endl;
	}
	else{
		string s0 = s;
		if(s0.size()==3) s0 = "0" + s0;
		else if(s0.size()==2) s0 = "00" + s0;
		else if(s0.size()==1) s0 = "000" + s0;
		
		while(1){
			res = max_trans(s0)- min_trans(s0);
			
			cout<<setw(4)<<setfill('0')<<max_trans(s0);
			cout<<" - ";
			cout<<setw(4)<<setfill('0')<<min_trans(s0);
			cout<<" = ";
			cout<<setw(4)<<setfill('0')<<res<<endl;
			
			if(res == 6174) break;
			
			s0 = too_string(res);
			if(s0.size()==3) s0 = "0" + s0;
		    else if(s0.size()==2) s0 = "00" + s0;
		    else if(s0.size()==1) s0 = "000" + s0;
			//cout<<"s0 === "<<s0<<endl;
		}
	}
	return 0;
}

//1019
#include <iostream>
#include <algorithm>
using namespace std;
 
int cmp(int a,int b){	//max to min 
	return a>b?1:0;
}
int main(){
	int n,a[4]={0},b,c,t;	cin>>n;
	t=n;
	do{
		a[0]=t/1000;
  		a[1]=t%1000/100;
		a[2]=t%1000%100/10;
		a[3]=t%10;
		sort(a,a+4,cmp);
		b=a[0]*1000	+a[1]*100+a[2]*10+a[3];
		sort(a,a+4);	//min to max
		c=a[0]*1000	+a[1]*100+a[2]*10+a[3];
		t=b-c;
		printf("%04d - %04d = %04d\n",b,c,t);
	}while(t!=6174&&t!=0000);
	return 0;
}