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, 10000).
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
#include<cstdio>#include<algorithm>using namespace std;bool cmp(int a,int b){ return a>b;}void toArray(int a,int b[]){ int mask=1000; for(int i=0;i<4;i++){ b[i]=a/mask; a%=mask; mask/=10; }}int toNum(int a[]){ int ans=0; for(int i=0;i<4;i++){ ans=ans*10+a[i]; } return ans;}int main(){ int a; scanf("%d",&a); int num[5],min,max; do{ toArray(a,num); sort(num,num+4); min=toNum(num); sort(num,num+4,cmp); max=toNum(num); a=max-min; printf("%04d - %04d = %04d/n",max,min,a); }while(a!=0&&a!=6174); return 0;}新闻热点
疑难解答
