PAT Class B-B1019 Digital Black Hole (20)

Given any 4-digit positive integer whose digits are not exactly the same, if we first sort the 4 numbers non-increasingly, then non-decreasingly, and then subtract the 2nd number from the 1st number, we will geta new number.Keep doing this over and over again, and we'll soon stop at 6174 known as the "digital black hole", the magic number also known as the Kaprekar constant.

For example, if we start with 6767, we will get

7766 - 6677 = 10899810 - 0189 = 96219621 - 1269 = 83528532 - 2358 = 61747641 - 1467 = 6174 …

Given any 4-digit positive integer, write a program to demonstrate the process of reaching a black hole.

input format:

The input gives a positive integer N in the interval (0,104).

Output format:

If all 4 digits of N are equal, output N - N = 0000 on one line; otherwise, output each step of the calculation on one line until 6174As difference occurs, see example for output format.Note that each number is output as 4 digits.

Input Sample 1:

6767

Output Sample 1:

7766 - 6677 = 10899810 - 0189 = 96219621 - 1269 = 83528532 - 2358 = 6174

Input Sample 2:

2222

Output Sample 2:

2222 - 2222 = 0000

#include#includeusing namespace std;string s1,s2;int main(){cin >> s1;int ans;//s1 may be less than 4 digits, 0 should be inserteds1.insert(0,4-s1.size(),'0');do{sort(s1.begin(), s1.end());s2 = s1;//s1 is from big to small at this timereverse(s1.begin(), s1.end());cout <原网站
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