题解 | 排序危机

#include<iostream>
using namespace std;
int main(){
    int n;
    cin >> n;
    string s;
    cin >> s;
    string lower,digit,upper;
    for(char c:s){
        if(c>='a'&&c<='z')lower+=c;
        else if(c>='0'&&c<='9')digit+=c;
        else if(c>='A'&&c<='Z')upper+=c;
    }
    cout << lower+digit+upper << endl;
    return 0;
}