Pat(A) 1069. The Black Hole of Numbers (20)
2017-08-18 00:11
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原题目:
原题链接:https://www.patest.cn/contests/pat-a-practise/10691069. The Black Hole of Numbers (20)
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
解题报告
题目是找出所有的数字黑洞。需要注意的是输出顺序以及本身就是特殊数字的情况。
代码
#include "stdio.h" #include <algorithm> #include <vector> using namespace std; int big(int num){ vector<int> arr; arr.push_back(num / 1000); arr.push_back(num / 100 % 10); arr.push_back(num / 10 % 10); arr.push_back(num % 10); sort(arr.begin(),arr.end()); return arr[3] * 1000 + arr[2] * 100 + arr[1] * 10 + arr[0]; } int small(int num){ vector<int> arr; arr.push_back(num / 1000); arr.push_back(num / 100 % 10); arr.push_back(num / 10 % 10); arr.push_back(num % 10); sort(arr.begin(),arr.end()); return arr[0] * 1000 + arr[1] * 100 + arr[2] * 10 + arr[3]; } int main(){ int num = 0; scanf("%d",&num); int b = big(num); int s = small(num); int newnum = b - s; if (num == newnum) printf("%04d - %04d = %04d\n",b,s,newnum); while(num != newnum){ printf("%04d - %04d = %04d\n",b,s,newnum); num = newnum; b = big(num); s = small(num); newnum = b - s; } //system("pause"); }
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