B1069 The Black Hole of Numbers

B1069 The Black Hole of Numbers (20分)

//注意数字处理时不足四位补上前导0.

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <cmath>
#include <math.h>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <stack>
#define lowbit(i)((i)&(-i))
using namespace std;
typedef long long ll;
const int MAX=3e5+10;
const int INF=0x3f3f3f3f;
const int MOD=1000000007;
const int SQR=632;//633块，632
bool cmp(char a,char b)
{
    return a>b;
}
bool cmp2(char a,char b)
{
    return a<b;
}
string change(int n)
{
    string ans="";
    while(n>0)
    {
       char c=n%10+'0';
       ans+=c;
       n/=10;
    }
    while(ans.size()<4)
        ans='0'+ans;
    return ans;
}
int change2(string x)
{
    int sum=0;
    for(int i=0;i<x.size();i++)
    {
        sum=sum*10+x[i]-'0';
    }
    return sum;
}
int main()
{
    int n;
    string a,b,temp;
    scanf("%d",&n);
    int t=n;
    while(1)
    {
    temp=change(t);
    sort(temp.begin(),temp.end(),cmp);
    a=temp;
    printf("%04d",change2(a));
    printf(" - ");
    sort(temp.begin(),temp.end(),cmp2);
    b=temp;
    printf("%04d",change2(b));
    printf(" = ");
    t=change2(a)-change2(b);
    printf("%04d\n",t);
    if(t==6174||t==0)
        break;
    }
    return 0;
}