PATB 1019 数字黑洞

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;

int num[5];

bool cmp(int a,int b){
    return a>b;
}

void to_array(int n){//n转化成数组,不用在意顺序反了
    for(int i=0;i<4;i++){
        num[i]=n%10;
        n/=10;
    }
}

int to_num(){
    int sum=0;
    for(int i=0;i<4;i++){
        sum*=10;
        sum+=num[i];
    }
    return sum;
}

int main()
{
    int N;
    scanf("%d",&N);
    while(1){
        to_array(N);
        int Max,Min;
        sort(num,num+4,cmp);
        Max=to_num();
        sort(num,num+4);
        Min=to_num();
        N=Max-Min;
        printf("%04d - %04d = %04d\n",Max,Min,N);
        if(N==0||N==6174)
            break;
    }
    return 0;
}