[c] Heap Question

[mackol]

i tried really hard to avoid posting this question but i cant seem to spot the problem :(

so here it is..

basically i want to print the highest number of 'search_counts' from a heap.

> there is an array of struct HEAP

> there is only 1 element in HEAP , it is DATA *dataPtr , basically it points to a struct DATA (which has been allocated memory dynamically)

> i have to delete the top most item from the heap ary and print it and then reheapDown to get it back to a heap form.

problem: it prints all but the last element correctly. for the last element it prints out garbage. :(

i have been through the debugger so many times but yet it failed.

here is the code

int j is the count of how many elements were inserted into the heap ary

int whatFn is basically a checker to see that if the number of elements inserted was less than the HEAP_SIZE which is 7 then use j otherwise use HEAP_SIZE for the restrictor

void printHeap1 (HEAP *ary, int j, int whatFn)
{
	int i = 0;
	HEAP *pWalker, *pCur, *pLast, dataOut;

	pCur = ary;

	printf("--- 7 Most popular searches ---\n");

	if (whatFn == NOT_EQUAL)
	{
  pLast = &ary[j];
  j--;
  for (pWalker = pCur; pWalker < pLast; pWalker++)
  {
 	 if (deleteHeap (ary, &j, &dataOut) == 1)
    printToScreen (&dataOut, "heap");
 	 else
    printf("Unable to delete node\n");
  }
	}
	else
	{
  pLast = &ary[HEAP_SIZE -1];
  j--;
  for (pWalker = pCur; pWalker < pLast; pWalker++)
  {
 	 if (deleteHeap (ary, &j, &dataOut) == 1)
    printToScreen (&dataOut, "heap");
 	 else
    printf("Unable to delete node\n");
  }
	}
	return;
}

this goes to the delete heap function that is

int deleteHeap (HEAP *heap, int *last, HEAP *dataOut)
{
//	int item;

	if (*last < 0)
	{
  return 0;
	}

	dataOut->dataPtr = heap[0].dataPtr;
	heap [0].dataPtr = heap [*last].dataPtr;
//	heap[*last].dataPtr = NULL;
	(*last)--;

	reheapDown (heap, 0, *last);

	return 1;
}

this later goes to the reheapDown function which is

void reheapDown (HEAP *heap, int root, int last)
{
	DATA hold, leftKey, rightKey, largeChildKey;
	int largeChildIndex = 0;
	//int parent;

	if ((root * 2 + 1) <= last)
	{
  leftKey = *(heap [root * 2 + 1].dataPtr);

  if ((root * 2 + 2) <= last)
  {
 	 rightKey = *(heap [root * 2 + 2].dataPtr);
  }
  else
  {
 	 rightKey.search_count = -1;
  }

  if (leftKey.search_count > rightKey.search_count)
  {
 	 largeChildKey = leftKey;
 	 largeChildIndex = root * 2 + 1;
  }
  else
  {
 	 largeChildKey = rightKey;
 	 largeChildIndex = root * 2 + 2;
  }

  if (heap[root].dataPtr->search_count < heap [largeChildIndex].dataPtr->search_count)
  {
 	 hold = *(heap [root].dataPtr);
 	 heap [root].dataPtr = heap [largeChildIndex].dataPtr;
 	 heap [largeChildIndex].dataPtr = &hold;

 	 reheapDown (heap, largeChildIndex, last);
  }
	}
	return;
}

any form of help is appreciated. i just need someone to spot the error. i can fix the rest myself

thanks :)

[mackol]

dont worry actually... i solved it :)

the error lied in the reheapDown function

the variable DATA hold was cauzing problems..

it should have been a pointer

DATA *hold

:)

[Gumboot]

Well done; that code makes my head spin :x :D

[mackol]

LOL :D it aint that bad ;)

[Gumboot]

Heh, I wasn't trying to diss your coding skills... ;) Lets just say that I sure am glad that pointers are on their way out. :)

[mackol]

i like pointers.. i like the fact that i am able to control the memory directly (well not exactly, but u know what i am saying), without coding in asm :)

besides, its a lot faster :)

[Gumboot]

You like them? Geez, how masochistic is that? :D

My personal opinion is that pointers:

1. Make code practically unreadable.

2. Rarely increase performance.

3. Don't really allow you to do anything that you couldn't already do.

4. Make it easy to introduce bugs.

I'm not denying that there are situations where pointers are absolutely necessary, but for the above reasons I would rather not use them. Thankfully, C# (my language of choice) allows you to avoid using pointers altogether (unlike C and C++). It still has them, mind you, but you are heavily discouraged from using them.

:alien:

[mackol]

i know it sounds crazy but once u get a hang of pointers it aint that bad.. :)

i havent tried C# yet... i will be doing C++ in jan and i already know c and beginning java and a little of actionscripting..

as u know, java and actionscripting dont have pointers (well, the do have them but they are hidden)

and its all cool but i still feel i have more control with the use of pointers.. i feel C and C++ form a stronger combo than what java and its rich APIs could present :)

its just my opinion derived from my 1 yr of programming experience :)