Converting a string of words of arbitrary size to an array of C strings

[vickyhu95]

Hello!
I am working on the below program right now. I am asked to convert a string of words to char array. The libraries included are the only few that I can use. Since main function can not be altered, I have to return an allocated double pointer char array to match the 'free'. Basically, I need helps on the function called "words_array". Thank you guys so much for any helps.

#include <iostream>
#include <fstream>
#include <sstream>
#include <string.h>//<cstring>
#include <cstdlib>

/**
 * Find number of words in s.
 * @param   count   number of words in s (separated by a space)
 * @param   sstream a string stream object
 * @param   l       a string that reads strings from stringstream
 * return   number of words in string s
 */
int words_of(std::string s) {
    int count = 0;
    std::string l;
    std::stringstream sstream(s);
    while (sstream >> l)    ++count;
    return count;
}

/**
 *  Convert string to character array of words.
 *  @param   s  string to convert
 *  @return     jagged array of words
 */
char **word_array(std::string s) {
    const char *array = s.c_str();
    char **charArray = (char**) malloc (sizeof(char) * (words_of(s)));
    strncpy(*charArray, array, sizeof(charArray));
    return charArray;
}

int main() {
    std::string files = "architecture.txt boolean.txt computers.txt kitties.txt";
    char **filenames = word_array(files);
    int n = words_of(files);
    for (int i=0; i<n; i++) {
        std::ofstream outfile(filenames[i]);
        outfile << "This is file " << i << std::endl;
        free(filenames[i]);
    }
    free(filenames);
    return 0;
}

[cire]

Since main function can not be altered, I have to return an allocated double pointer char array to match the 'free'.

The fact that there are multiple frees in main should clue you in to something.