题解

#include<iostream>
#include<string>
#include<algorithm>
using namespace std;
int main(){
    string s,s1,s2,s3,s4;
    cin>>s;
    for(int i=0;i<s.size();i++){
        if(s[i]>='a'&&s[i]<='z'){
            s1+=s[i];
        }else if(s[i]>='A'&&s[i]<='Z'){
            s2+=s[i];
        }else if(s[i]>='0'&&s[i]<='9'){
            s3+=s[i];
        }else{
            s4+=s[i];
        }
    }
    sort(s1.begin(),s1.end());
    sort(s2.begin(),s2.end());
    sort(s3.begin(),s3.end());
    sort(s4.begin(),s4.end());
    cout<<s1<<s2<<s3<<s4;
    return 0;
}