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:
6767
Sample Output 1:
7766 - 6677 = 1089
9810 - 0189 = 9621
9621 - 1269 = 8352
8532 - 2358 = 6174
Sample Input 2:
2222
Sample Output 2:
2222 - 2222 = 0000
思路 俩个坑点 一个是 输入的时候不是4位数字 , 另一个是 6174 也需要输出 一行 不能无结果。
code
#pragma warning(disable:4996)
#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
bool cmp(const int& a, const int& b) {
return a > b;
}
int covert(string& s) {
int sum = 0;
for (int i = 0; i < 4; ++i) {
sum *= 10;
sum += (s[i] - '0');
}
return sum;
}
string decover(int x) {
string res;
for (int i = 0; i < 4; ++i) {
res += (x % 10 + '0');
x /= 10;
}
string dres(res.rbegin(), res.rend());
return dres;
}
int main(){
int n;
cin >> n;
string s;
s = decover(n);
if (s[0] == s[1] && s[1] == s[2] && s[2] == s[3]) {
cout << s << " - " << s << " = " << "0000" << endl;
}
else {
do{
sort(s.begin(), s.end(), cmp);
cout << s << " - ";
int a = covert(s);
sort(s.begin(), s.end());
cout << s << " = ";
int b = covert(s);
int dif = a - b;
s = decover(dif);
cout << s << endl;
} while (s != "6174");
}
system("pause");
return 0;
}