Hi All,
I would like to keep an array the same even after it is passed into a function. I am doing different sorts on the same data but when i try using
where n is the total number in the array and num is an array.Code:num=temp HeapSort(temp,n);
When I try using this, num and temp is sorted completed. Not sure why. Is there anyway to keep num the same after a function is used on it. I am not using any pointers by the way.
I very much doubt that!Originally Posted by Ramkiller1
arrays cannot be used as lvalues: thay cannot be assigned to.
I believe both num and temp are pointers (you might like to read the comp.lang.c. FAQ, especially section 6).
The pointers point to the same memory. Whatever you do through one pointer is visible through the other.
Is there any solution to my issue then?
Make a copy of the array and pass the copy to the function.
thats why i used temp=num;
But it did not work. It was used like a pointer
You have to make a separate copy in memory so that there are two arrays. A pointer to the original array will just make an alias for that array.
Any code come to mind?
Try writing it yourself. First, allocate some memory, then copy the original array into the new array. Free the new array when you are done with it.
Will Do
Well i just did this
This did the same thing as using temp. Unless I copied it wrongly.Code:int * p; p=(int *)malloc(max*sizeof(int)); //Allocate size of array p=num; sort1(p,n); free(p);
You copied wrongly. What you did is set the pointer to point to the first element of the array, after having allocated memory that the pointer points to. Effectively, all you did was create a memory leak, and the free(p) results in undefined behaviour or a later double free error.
Rather:
Code:int *p = malloc(max * sizeof(*p)); /* Loop over the elements of num and assign them to the elements of p */ /* ... */ sort1(p, n); free(p);
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Thanks it worked, Guess I was thinking of it wrongly. Did I need to make a pointer then for this or just another array or are you showing me how to save space ?
If you want to use dynamic memory allocation, then a pointer was the right approach. If not, another array of at least the same size would work. You cannot save space because you need to copy those elements.
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Once you made a second array, I think that the function which you are after is memcpy().
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