#include <iostream>
#include <sstream>
using namespace std;
   
int power(int a, int n)
{
    int res = 1;
    for (int i = 0; i < n; ++i)
    {
        res *= a;
    }
    return res;
}
   
int compare(const void * a, const void * b)
{
    return *(int*)a - *(int*) b;
}
   
int nonIncrese(int n)
{
    int digits[4];
    digits[0] = n % 10;
    digits[1] = n / 10 % 10;
    digits[2] = n / 100 % 10;
    digits[3] = n / 1000;
    qsort(digits, 4, sizeof(int), compare);
       
    int res = 0;
    for (int i = 0; i < 4; ++i)
    {
        res += digits[i] * power(10, i);
    }
   
    return res; 
}
   
int nonDecrese(int n)
{
    int digits[4];
    digits[0] = n % 10;
    digits[1] = n / 10 % 10;
    digits[2] = n / 100 % 10;
    digits[3] = n / 1000;
    qsort(digits, 4, sizeof(int), compare);
       
    int res = 0;
    for (int i = 0; i < 4; ++i)
    {
        res += digits[3-i] * power(10, i);
    }
   
    return res; 
   
}
   
string toString(int n)
{
    string sn = static_cast<ostringstream*>( &(ostringstream() << n) )->str();
    if (n < 10){
        string s0 = "000";
        return s0.append(sn);
    }
    if (n < 100){
        string s0 = "00";
        return s0.append(sn);
    }
    if (n < 1000)
    {
        string s0 = "0";
        return s0.append(sn);
    }
    return sn;
}
   
int main()
{
    int N;
    cin >> N;
    // N >= 1000, N <= 9999
    if (N % 1111 == 0)
    {
        cout << N << " - " << N << " = " << "0000" << endl;
    }
    else if (N == 6174)
    {
        cout << "7641 - 1467 = 6174" << endl;
    }
    else{
        int n = N;
        while (n != 6174){
            cout << toString(nonIncrese(n)) << " - " << toString(nonDecrese(n)) << " = " << toString(nonIncrese(n) - nonDecrese(n)) << endl;    
            n = nonIncrese(n) - nonDecrese(n);
   
        }
    }
       
    return 0;
}

我的代码：

#include<stdio.h>

int main(int argc,char *argv[])
{
	int n,temp;
	int max,min;
	int i,j;
	int arr[4];
	scanf("%d",&n);
    do
	{
		max=0;
		min=0;
		for(i=0;i<4;i++)
		{
			arr[i]=n%10;
			n=n/10;
		}
		for(i=1;i<4;i++)
			for(j=0;j<4-i;j++)
			{
				if(arr[j]>arr[j+1])
				{
					temp=arr[j];
					arr[j]=arr[j+1];
					arr[j+1]=temp;
				}
			}
		for(i=0;i<4;i++)
			min=min*10+arr[i];
		for(j=3;j>=0;j--)
			max=max*10+arr[j];
		n=max-min;
		printf("%.4d - %.4d= %.4d\n",max,min,n);
	}while(n!=6174&&n!=0);

	return 0;
}

求高手指点迷津啊。。。