SRC/heapsort.c File Reference

#include "heapsort.h"

Include dependency graph for heapsort.c:

Go to the source code of this file.

Functions
static void	add_to_sort_heap (int *heap, float *sort_values, int index, int heap_tail)
static int	get_top_of_heap_index (int *heap, float *sort_values, int heap_tail)
void	heapsort (int *sort_index, float *sort_values, int nelem)

---

Function Documentation

static void add_to_sort_heap	(	int *	heap,
		float *	sort_values,
		int	index,
		int	heap_tail
	)			[static]

Definition at line 46 of file heapsort.c.

{

/* Adds element index, with value = sort_values[index] to the heap.          *
 * Heap_tail is the number of elements in the heap *after* the insert.       */

    unsigned int ifrom, ito;    /* Making these unsigned helps compiler opts. */
    int temp;

    heap[heap_tail] = index;
    ifrom = heap_tail;
    ito = ifrom / 2;

    while(ito >= 1 && sort_values[heap[ifrom]] < sort_values[heap[ito]])
        {
            temp = heap[ito];
            heap[ito] = heap[ifrom];
            heap[ifrom] = temp;
            ifrom = ito;
            ito = ifrom / 2;
        }
}

Here is the caller graph for this function:

static int get_top_of_heap_index	(	int *	heap,
		float *	sort_values,
		int	heap_tail
	)			[static]

Definition at line 74 of file heapsort.c.

{

/* Returns the index of the item at the top of the heap (the smallest one).  *
 * It then rebuilds the heap.  Heap_tail is the number of items on the heap  *
 * before the top item is deleted.                                           */

    int index_of_smallest, temp;
    unsigned int ifrom, ito, heap_end;

    index_of_smallest = heap[1];
    heap[1] = heap[heap_tail];
    heap_end = heap_tail - 1;   /* One item deleted. */
    ifrom = 1;
    ito = 2 * ifrom;

    while(ito <= heap_end)
        {
            if(sort_values[heap[ito + 1]] < sort_values[heap[ito]])
                ito++;

            if(sort_values[heap[ito]] > sort_values[heap[ifrom]])
                break;

            temp = heap[ito];
            heap[ito] = heap[ifrom];
            heap[ifrom] = temp;
            ifrom = ito;
            ito = 2 * ifrom;
        }

    return (index_of_smallest);
}

Here is the caller graph for this function:

void heapsort	(	int *	sort_index,
		float *	sort_values,
		int	nelem
	)

Definition at line 19 of file heapsort.c.

{

/* This routine loads sort_index [1..nelem] with nelem values:  the indices  *
 * of the sort_values [1..nelem] array that lead to sort_values[index] being *
 * decreasing as one goes through sort_index.  Sort_values is not changed.   */

    int i;

/* Build a heap with the *smallest* element at the top. */

    for(i = 1; i <= nelem; i++)
        add_to_sort_heap(sort_index, sort_values, i, i);

/* Now pull items off the heap, smallest first.  As the heap (in sort_index) *
 * shrinks, I store the item pulled off (the smallest) in sort_index,        *
 * starting from the end. The heap and the stored smallest values never      *
 * overlap, so I get a nice sort-in-place.                                   */

    for(i = nelem; i >= 1; i--)
        sort_index[i] = get_top_of_heap_index(sort_index, sort_values, i);
}

Here is the call graph for this function:

Here is the caller graph for this function: