Răspuns:
#include <bits/stdc++.h>
#include <string>
using namespace std;
int main() {
char s[999]; cin.getline(s,998,'\n');
for(int i=0;i<strlen(s);i++) {
if(strchr("aeiouAEIOU",s[i])) {
cout<<s[i]<<'*';
}
else {
cout<<s[i];
}
}
}
Codul a fost verificat cu succes.