都是这么做的？+1

#include<bits/stdc++.h>
using namespace std;
void aco(vector<char>v){
    for(int i=0;i<v.size();i++){
        cout<<v[i];
    }
}
int main(){
    vector<char>a,b,c,d;
    string s;
    cin>>s;
    for(int i=0;i<s.size();i++){
        if(isalpha(s[i])){
            if(s[i]>=97)a.push_back(s[i]);
            else b.push_back(s[i]);
        }else if(isdigit(s[i])){
            c.push_back(s[i]);
        }else d.push_back(s[i]);
    }sort(a.begin(),a.end());
    sort(b.begin(),b.end());
    sort(c.begin(),c.end());
    sort(d.begin(),d.end());
    aco(a),aco(b),aco(c),aco(d);
}