PTA甲级考试真题练习69——1069 The Black Hole of Numbers

题目

思路

水题，利用sprintf和sscanf进行字符串和整数的格式转换

代码

#include <iostream>
#include<algorithm>
using namespace std;
bool cmp(char a, char b) {
	return a > b;
}
int main() {
	int n;
	cin >> n;
	char num[5];
	sprintf_s(num, "%04d", n);
	int k = num[0];
	bool bd = false;
	for (int i = 1; i < 4; ++i) {
		if (num[i] != k) {
			bd = true;
			break;
		}
	}
	if (!bd) {
		cout << num << " - " << num << " = 0000";
		return 0;
	}
	int ans = 0;
	while (ans != 6174) {
		int num1, num2;
		sort(num,num+4);
		sscanf_s(num, "%04d", &num1);
		sort(num,num+4,cmp);
		sscanf_s(num, "%04d", &num2);
		ans = num2 - num1;
		printf("%04d - %04d = %04d\n", num2, num1, ans);
		sprintf_s(num, "%04d", ans);
	}
	return 0;
}