C++ Error while attempting to iteratively return string

Question

I am attempting to return a reversed version of the string "Loyce" in an iterative function. The program runs, but it crashes after running. Any help would be appreciated.

string Iterative4(string word)
{
    for(int x = 0; x < word.length(); x++)
    {
        if (word.length() - 1 > 0)
        {
            char last_char = word[word.length() - 1];
            word.erase(word.length() - 1);
            string go = Iterative4(word);
            return go;
        }
    }

}

int main() {
    cout << Iterative4("Loyce") << endl;
}

Your Iterative4 appears to be both iterative and recursive. I'm guessing that's not really what you want. — Jerry Coffin
– Jerry Coffin, Commented Oct 15, 2014 at 0:10
@JonathanPotter To me, it looks like a homework assignment, where this is the "fourth implementation" of the same problem (reversing a string) in an iterative way. If this is true, std::reverse is of course no option (or maybe to be used in one of the implementations they should do). — leemes
– leemes, Commented Oct 15, 2014 at 0:11
I see a few problems: First, what is the outer loop for if you never use x? You call your function Iterative4 recursively, so, probably, you solved problem recursively before and that is an artifact of your changes? Do something with x instead. Second, you erase the last character from word, then you don't do anything with it. It will be lost. Since you want to reverse the string, I guess it's not too difficult for you to guess where you should put it ;-) — Oguk
– Oguk, Commented Oct 15, 2014 at 0:16

Etixpp · Accepted Answer · 2014-10-15 00:58:37Z

1

Use the at function of string. Do not use recursive and iterative together.

string Iterative4 ( const string& word )
{
    std::string l_bla;
    bla.reserve(word.size());
    for ( string::size_type x = word.length ( ); x > 0; x-- )
    {

        l_bla += word.at ( x -1 );

    }
    return l_bla;
}

this should work, but i didnt test it, maybe you have to change something small

EDIT: Tested now and it works perfectly

edited Oct 15, 2014 at 0:58

answered Oct 15, 2014 at 0:17

Etixpp

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7 Comments

Neil Kirk Over a year ago

Pass word by const reference.

Neil Kirk Over a year ago

Reserve l_bla to word's size.

Etixpp Over a year ago

Well i think thats a unnecesarry improvement @ this point, but year, i can do it

Neil Kirk Over a year ago

It's actually a better improvement than the first one.

Neil Kirk Over a year ago

It looks correct to me. The only remaining issue is if the string size is too big for int, but we can live with it.

|

Chris Culter · Accepted Answer · 2014-10-15 00:15:06Z

0

One immediate problem is like that if word.length() - 1 is not greater than 0, then the function Iterative4 fails to return a value. Since the function is declared to return a string, this results in undefined behavior, which may include a crash.

answered Oct 15, 2014 at 0:15

Chris Culter

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Comments

dif · Accepted Answer · 2014-10-15 01:15:32Z

0

string Iterative4(string word)
{
    if (word.length() - 1 > 0)
    {
        char last_char = word[word.length() - 1];
        word.erase(word.length() - 1);
        string go = Iterative4(word);
        return go;
    }
    else
        return word;
}

int main() {
    cout << Iterative4("Loyce") << endl;
}

I didn't test it.

If you insist on recursion, these or sth like these should work.

As a homework, it's just fine.

But if you are to do some real work, it should be noticed that recursion is a very very expensive action.

answered Oct 15, 2014 at 1:15

dif

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