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Deleting all consonants from a string using recursion in c++

I'm almost completely new to programming and I try to learn C++. This is the first task where I feel like I hit a wall. I tried to search but because people usually use a loop to solve the problem I could not find anything.

I tried to find a recursive solution to delete all consonants from a string (I think I know how to solve it using loops, but wanted to expand my knowledge on recursion).

#include <iostream>
#include <string>

using namespace std;

int i = 0;
string s("");

string del_cons(string z){
if(i == (z.length()-1) ){
s+= z.substr(i);
return s;
}
else if(z[i] == 'a' || z[i] == 'e' || z[i] == 'i' || z[i] == 'o' || z[i] == 'u'){
i++;
s+= del_cons(z.substr(i));
return s;
}
else{
s+= z.substr(i,1);
i++;
s+= del_cons(z.substr(i));
return s;
}
}


int main(){
string x;
getline(cin, x);

cout << del_cons(x) << endl;

return 0;
}


The code compiles, but when trying it out with a string, I get this error message:

terminate called after throwing an instance of 'std::out_of_range'
what(): basic_string::substr: __pos (which is 3) > this->size() (which is 2)
Abgebrochen (Speicherabzug geschrieben)

When playing around with the code, this line seems to be the problem:

s+= del_cons(z.substr(i));


Could somebody give me a hint what I'm doing wrong? It seems I'm misusing the substr() function, but I don't know how. Thanks a lot.

1 Answer
1

Sorry but I could not resist...

#include <string>
#include <iostream>
#include <algorithm>

int main()
{
std::string s;
std::getline( std::cin, s );
s.erase( std::remove_if( s.begin(),
s.end(),
(unsigned char x){ return ! ( x == 'a' || x == 'e' || x == 'i' || x == 'o' || x == 'u' ); }
),
s.end()
);
std::cout << s << std::endl;
}


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