Question

I’m trying to loop through a list of strings and find where a given character is located at in said string. I then store the string in a given vector based on where/if the character occurs. I’m getting a runtime error in the following code before the loop finishes executing. I’ve looked over the it half a dozen times already and can’t seem to find anything wrong.

vector< vector<string> > p;
for(list< string >::iterator ix = dictionary.begin(); ix != dictionary.end(); ix++)
{
    int index = contains(*ix, guess);
    index++;

    p.at(index).push_back(*ix); //0 will contain all the words that do not contain the letter
                                //1 will be the words that start with the char
                                //2 will be the words that contain the the char as the second letter
                                //etc...
}



int contains(string str, char c)
{
    char *a = (char *)str.c_str();
    for(int i = 0; i < (str.size() + 1); i++)
    {
        if(a[i] == c)
            return i;
    }
    return -1;
}

Answer 1

vector< vector > p defines p as empty vector. You must have vector elements added to it before using vector::at().
For example:

const size_t MAX_LETTERS_IN_WORD = 30;
vector< vector<string> > p(MAX_LETTERS_IN_WORD);

/* same as before */

As an alternative you can check p.size() before using at() and push_back() additional elements into p as needed