Heap Sort Infinite Loop

[Pkmnmster]

I am trying to understand what is going wrong with my heap sort. It compiles, populates the vector, prints it and gets to this one particular method call and I can't seem to track the issue for the life of me. I implemented Wikipedias psudo-code to try to get it to work but I just can't figure it out. Hopefully you all can help me spot why its taking x>10 minutes and still not finishing. Its probably looping somewhere...

// Heap Sort method

void
heapSort(vector <int>& sortablevector, size_t count)
{

	make_vector_heap(sortablevector, count);
	
	size_t end = count-1; //in languages with zero-based arrays the children are 2*i+1 and 2*i+2
    while ( end > 0 )
	{
        //(swap the root(maximum value) of the heap with the last element of the heap)
         
		swap( sortablevector[end], sortablevector[0] );
		 
         //(decrease the size of the heap by one so that the previous max value will
         //stay in its proper placement) 
         end = end - 1;
		 
         //(put the heap back in max-heap order)
         downHeap( sortablevector, 0, end );
		 
	}
	
}

// My version of wikipedia's 'Heapify' method

void
make_vector_heap(vector <int>& sortablevector, size_t count)
{

	size_t start = ( count - 1) / 2;
     
    while ( start >= 0 )
	{
        //(sift down the node at index start to the proper place such that all nodes below
        //the start index are in heap order)
		 
        downHeap(sortablevector, start, count-1 );
        start = start - 1;
	
	}
}

//my version of wikipedias 'siftdown' method

void
downHeap(vector <int>& v, size_t start, size_t end)
{
	
	size_t root = start;

	while ( ( root * 2 ) + 1 <= end )
	{
		size_t child = ( root * 2 ) + 1;
        size_t numswap = root;        
         
        if ( v[numswap] < v[child] )
		{
             numswap = child;
		}
		if ( ( child + 1 <= end ) && ( v[numswap] < v[child + 1 ] ) )
		{
         
			numswap = child + 1;
         
		}
		if (numswap != root)
		{
		 
             swap( v[root], v[numswap] );
             root = numswap;
			 
		}else{
		
			break;
		
		}
	
	}
}

Hopefully this makes sense? Any help is appriciated! Thanks :)

[Pkmnmster]

Maybe someone will actually see this now. Help would be greatly appriciated. Thanks.

[TheIdeasMan]

By far the quickest & easiest way to solve run time problems is to use a debugger. Should be easy if you are using an IDE. Step through the code 1 line at a time, keep an eye on the value of your variables to deduce where it all goes wrong.

Found this code with a google search ( heap sort C++ example )- don't know how good it is. Some of the others returned by google weren't very goodIMO.

http://crackprogramming.blogspot.com.au/2012/11/heap-sort-c-implementation.html

Maybe you can compare to your code.

Cheers

Edit: A really minor thing :

This :

start = start - 1;

can be written :

start--; // decrementing
start++;  // incrementing

if not decrementing by 1, then use:

start -= 2;  // start = start -2
start += 2  // start = start + 2 

There are other assignment operators as well.