Manipolazione stringhe

#include
#include
#include

using namespace std;

int main()
{
string str="abcdefghijklmnopqrstuvwxyz";
string str1,str2,str3,str_app;
//char vocali[]={a,e,i,o,u};
unsigned int i,c;
char a='1';
float fu,sum;
cout

for(i=0;i if((str.at(i)=='a' || str.at(i)=='e' || str.at(i)=='i' || str.at(i)=='o' || str.at(i)=='u' )){
str.at(i)=a;
a++;
}

str1=str.substr(0,10);
str2=str.substr(10,10);
str3=str.substr(20,10);

cout str_app=str2;
str2=str3;
str3=str1;
str1=str_app;

getline( cin, str2 );
fu = atof(str2.c_str()); //13.2
sum=100.0f+fu;
//cout /*
//stampa stringa 2 al contrario
string app="abcdefghi";
cout str2=str_app;
c=str2.length();
for(i=0;i app.at(i)=str2.at(c);
str2.at(c)=str2.at(i);
str2.at(i)=app.at(i);
}
*/
cout

//punto h
str2+=2;
cout //--------------
str=str1+str2+str3;
cout //posizione della lettera n;
for(i=0;i if(str.at(i)=='n'){
c=i;
break;
}
cout

str.replace(10,7,"aa");
str.erase(3,5);
cout

return 0;
}