How to replace specific characters in a string with other characters

Question

I am trying to make a program that will take as input a string and replace all the vowels with the * symbol. So, for \"hello world\", star_vowels should return \"h*ll* w*rld

Answer 1

By incrementing the j at the beginning you will lose the 0 index (the first character).

Since you want to return new data to the outside world (outside the function scope), you either allocate memory for the new data outside the function, and pass in a pointer of that data to this function, or you just allocate dynamic memory inside this function - remember to delete it.

One implementation would be:

char *star_vowels(char s[]){
    // let's allocate memory for the new string.
    // its size should be strlen(s) + 1 (the ending char).
    char *final = malloc(strlen(s) + 1); 

    int j = 0;
    while (s[j] != 0){
        if (s[j] == 'a' || s[j] == 'e' || s[j] == 'i' || s[j] == 'o' || s[j] == 'u'){
            final[j] = '*';
        } else {
            final[j] = s[j];
        }
        j++;
    }
    final[j] = 0; // end the string
    return final;
}

Working example: http://codepad.org/dd2w5cuy