PAT 乙级 1019

当且仅当差为6174才不满足循环条件；

#include<iostream>#include<algorithm>using namespace std;bool cmp(int a,int b){return a>b;}int main(){int a[4];int n;cin>>n;a[0]=n/1000;a[1]=n/100%10;a[2]=n/10%10;a[3]=n%10;int flag=0;for(;flag!=1;){//cout<<"hello world"<<endl;if(a[0]==a[1]&&a[0]==a[2]&&a[0]==a[3]){cout<<a[0]<<a[1]<<a[2]<<a[3]<<" - "<<a[0]<<a[1]<<a[2]<<a[3]<<" = ";printf("%04d\n",0);break ;}else {sort(a,a+4,cmp);cout<<a[0]<<a[1]<<a[2]<<a[3]<<" - "<<a[3]<<a[2]<<a[1]<<a[0]<<" = ";n=a[0]*1000+a[1]*100+a[2]*10+a[3]-a[3]*1000-a[2]*100-a[1]*10-a[0];printf("%04d\n",n);a[0]=n/1000;        a[1]=n/100%10;        a[2]=n/10%10;        a[3]=n%10;        if(a[0]==6&&a[1]==1&&a[2]==7&&a[3]==4){flag=1;}}//else }return 0;}