Thread: Help with struct code!

  1. #1
    Registered User
    Join Date
    May 2013

    Lightbulb Help with struct code!

    I am writing a program that expands array list whenever they get too full

    so far i have this:

    #define DEFAULT 10
    typedef struct ArrayList
        //array of strings
        char **array;
        //number of elements that have been added to the array
        int elements;
        // maximum length of array
        int maximum;
    } ArrayList;
    ArrayList *myList(int length)
        int i;
        //dynamically allocates space for a new ArrayList named list
        ArrayList *list;
        list = (ArrayList*)malloc(sizeof(ArrayList));
        //dynamically allocates space for array of size LENGTH or DEFAULT(whichever is greater)
        if(DEFAULT < length){
            list->array = malloc(sizeof(char *) * length);
            list->array = malloc(sizeof(char *) * DEFAULT);
        //initialize pointers in array to NULL with length
    if(DEFAULT < length){
            for(i=0; i<length; i++){
                list->array[i] == NULL;
    //set the size and capacity
        list->elements = 0;
        list->maximum = array[i];
        //print out the size of list
        printf("Created new ArrayList of size %d.\n", maximum);
        //return function
        return list;
    So, ArrayList *myList should return a pointer to the new arraylist or null if malloc fails.

    I am confused on what exactly I need to set my maximum to, I know that it shouldn't be 0 and array[i] doesn't seem to be working either. I also am not sure if I am properly setting up null correctly for my array. If there is anything with my code that seems wrong please do point it out as I have been staring at this for hours and am really trying to understand this but I keep hitting a wall.


  2. #2
    Registered User
    Join Date
    Aug 2005
    For me it would be logical to set maximum to the number of char * you have actually allocated.
    e.g. whatever is greater DEFAULT or length.
    So I would set list->maximum before initializing the pointers to NULL and then initialize from 0 to < list->maximum

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