1069. The Black Hole of Numbers (20)【模拟】——PAT (Advanced Level) Practise
2017-07-26 11:31
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题目信息
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
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
解题思路
直接计算就可以AC代码
#include <cstdio> #include <algorithm> using namespace std; int getmin(int a){ int t[4] = {0}, c = 0; while (a){ t[c++] = a%10; a /= 10; } sort(t, t + 4); c = 0; while (c < 4){ a = a*10 + t[c++]; } return a; } int getmax(int a){ int t[4] = {0}, c = 0; while (a){ t[c++] = a%10; a /= 10; } sort(t, t + 4, greater<int>()); c = 0; while (c < 4){ a = a*10 + t[c++]; } return a; } int main() { int a; scanf("%d", &a); while (true){ int mn = getmin(a); int mx = getmax(a); printf("%04d - %04d = %04d\n", mx, mn, mx - mn); a = mx - mn; if (a == 6174 || mn%10 == mn/1000) break; } return 0; }
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