How to declare an array with an arbitrary size

Question

Ok, this is a C programming homework question. But I\'m truly stuck.

I ask the user to input words, and then I insert the input into an array, but I can\'t have any

Answer 1

You can malloc a block of memory large enough to hold a certain number of array items.

Then, before you exceed that number, you can use realloc to make the memory block bigger.

Here's a bit of C code that shows this in action, reallocating an integer array whenever it's too small to hold the next integer.

#include 
#include 

int main (void) {
    int *xyzzy = NULL;   // Initially NULL so first realloc is a malloc.
    int currsz = 0;      // Current capacity.
    int i;

    // Add ten integers.

    for (i = 0; i < 10; i++) {
        // If this one will exceed capacity.

        if (i >= currsz) {
            // Increase capacity by four and re-allocate.

            currsz += 4;
            xyzzy = realloc (xyzzy, sizeof(int) * currsz);
                // Should really check for failure here.
        }

        // Store number.

        xyzzy[i] = 100 + i;
    }

    // Output capacity and values.

    printf ("CurrSz = %d, values =", currsz);
    for (i = 0; i < 10; i++) {
        printf (" %d", xyzzy[i]);
    }
    printf ("\n");

    return 0;
}