PAT(甲级)1069
2015-09-29 10:32
337 查看
1069. The Black Hole of Numbers (20)
时间限制100 ms
内存限制
65536 kB
代码长度限制
16000 B
判题程序
Standard
作者
CHEN, Yue
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 <iostream> #include <cstring> #include <algorithm> using namespace std; bool cmp(const char &ch1,const char &ch2 ){ return ch1 > ch2; } void myitostr(int n,char str1[]){ int i=3; while(n){ str1[i] = n%10+'0'; n /=10; i--; } for(;i>=0;i--) str1[i]='0'; str1[4] = '\0'; } int main(){ int n; char str1[6]; char str2[6]; char res[6]; cin >>n; myitostr(n,str1); strcpy(str2,str1); sort(str1,str1+4); sort(str2,str2+4,cmp); int num1=atoi(str1); int num2=atoi(str2); n=num2-num1; if(n==0){ cout <<str2 <<" - " <<str1 <<" = "; myitostr(n,res); cout <<res <<endl; return 0; } while(1){ cout <<str2 <<" - " <<str1 <<" = "; myitostr(n,res); cout <<res <<endl; if(n==6174) return 0; myitostr(n,str1); strcpy(str2,str1); sort(str1,str1+4); sort(str2,str2+4,cmp); num1=atoi(str1); num2=atoi(str2); n=num2-num1; } }
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