B1019 数字黑洞 /A1069 The Black Hole of Numbers

题目：https://pintia.cn/problem-sets/994805260223102976/problems/994805302786899968

思路理清以后就很简单了，主要一开始各部分的功能顺序没有想好，这题应该是必须要用数组的把

代码

#include<algorithm>
#include<vector>
#include<iostream>
using namespace std;
int convert(int &num){
    vector<int> list(4);
    for(int i = 0; i < 4; i++){
        list[i] = num % 10;
        num /= 10;
    }
    sort(list.begin(),list.end());
    int temp = list[0]*1000 + list[1]*100 + list[2]*10 + list[3];
    num = list[3]*1000 + list[2]*100 + list[1]*10 + list[0];
    return temp;
}
int main(){
    int n1, n2, result = -1;
    scanf("%d",&n1);
    while(result != 0&&result!=6174){
        n2 = convert(n1);
        result = n1 - n2;
        printf("%04d - %04d = %04d\n", n1, n2, result);
        n1 = result;
    }
}