dynamic array representaion

[gju]

hi guys,

i am not able to declare the array dynamically in c will you help me out thanks

[Narue]

What did you try? While it's straightforward, the exact method depends on the result you want.

[gju]

hi
actully i want to impliment stack in c using array and i want to double the size of array as it fills completely so please help me out

[N1GHTS]

For dynamically sized arrays in C, your friend is the realloc() function. But instead of int a[5], you must use int *a = malloc(5 * sizeof(int));. Only then can you use the realloc() function to resize the array. In other words...

int *Array = (int *) malloc(3 * sizeof(int));  // Create an array with 3 ints

Array[0] = 11;
Array[1] = 250;
Array[2] = 7;

// Now I want to increase its size...

Array = (int *) realloc(Array, 5 * sizeof(int));  // I've now reallocated the array to 5 ints

Array[3] = 9;
Array[4] = 999;

Reallocating should only be done when absolutely necessary. This is because there is a highly possible performance hit using this function as it needs to find a place in memory where the data can fit. In other words, if the array cannot grow in its place, realloc() will find a new place and copy the data to the new place. Doing this too much can be costly in clock cycles.

[abhimanipal]

Just a small addition to the above post.
When ever you declare arrays dynamically you must

int main()
{
        int *arr =(int *)malloc(sizeof(int)*10);

        if(!arr){
                // Check if you did get the memory you asked for
                printf("No memory. Terminating program\n");
                exit(1);
        }
        else{
                printf("Sufficient memory found\n");
        }

        // Do operation on the array here

        free(arr);                     // Free the memory that was given to you after you are done using it 
        return 0;
}