PAT 1069 The Black Hole of Numbers[简单]

1069 The Black Hole of Numbers（20 分）

For any 4-digit integer except the ones with all the digits being the same, if we sort the digits in non-increasing order first, and then in non-decreasing order, a new number can be obtained by taking the second number from the first one. Repeat in this manner we will soon end up at the number 6174 -- the black hole of 4-digit numbers. This number is named Kaprekar Constant.

For example, start from 6767, we'll get:

7766 - 6677 = 1089

9810 - 0189 = 9621

9621 - 1269 = 8352

8532 - 2358 = 6174

7641 - 1467 = 6174

... ...

Given any 4-digit number, you are supposed to illustrate the way it gets into the black hole.

Input Specification:

Each input file contains one test case which gives a positive integer N in the range (0,104).

Output Specification:

If all the 4 digits of N are the same, print in one line the equation N - N = 0000. Else print each step of calculation in a line until 6174 comes out as the difference. All the numbers must be printed as 4-digit numbers.

Sample Input 1:

Sample Output 1:

7766 - 6677 = 1089

9810 - 0189 = 9621

9621 - 1269 = 8352

8532 - 2358 = 6174

Sample Input 2:

Sample Output 2:

2222 - 2222 = 0000

题目大意：给定一个四位数，展示出每位数从大到小排列，与从小到大排列的差值，直到出现6174黑洞数停止。

//这道题目是简单的，但是还是遇见了一些问题：

AC：

#include <iostream>

#include <algorithm>

#include <vector>

#include <stdlib.h>

#include<cstdio>

using namespace std;

int main()

{

    int n;

    cin>>n;

    int a[],big,small,res=-;

    int temp=;

    while(res!=)

    {

        fill(a,a+,);

        while(n!=)

        {

            a[temp++]=n%;

            n/=;

            //cout<<"kk";

        }

        temp=;

        sort(a,a+);//默认从小到大排列

        small=a[]*+a[]*+a[]*+a[];

        big=a[]*+a[]*+a[]*+a[];

        if(a[]==a[]&&a[]==a[]&&a[]==a[])

        {

            printf("%04d - %04d = 0000\n",big,small);

            return ;

        }

        res=big-small;

        printf("%04d - %04d = %04d\n",big,small,res);

        n=res;

    }

    return ;

}

1.第一次忽略了temp=0；应该在使用过后将其赋值为0的；

2. 应该将a数组初始化为0，要不然下次会有影响的，比如在有0位的时候：

3.最后就是提交发现第0个测试点过不去，原来是因为相同数的时候只输出了0，而不是0000！

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