/*Functions and structures for implementing a minimizing priority queue.Copyright (C) 2006  Rob Hess <hess@eecs.oregonstate.edu>@version 1.1.1-20070330*/#include "minpq.h"#include "utils.h"#include <limits.h>

/************************* Local Function Prototypes *************************/void restore_minpq_order( struct pq_node*, int, int );void decrease_pq_node_key( struct pq_node*, int, int );/************************** Local Inline Functions ***************************//* returns the array index of element i's parent */static __inline int parent( int i ){	return ( i - 1 ) / 2;}/* returns the array index of element i's right child */static __inline int right( int i ){	return 2 * i + 2;}/* returns the array index of element i's left child */static __inline int left( int i ){	return 2 * i + 1;}/********************** Functions prototyped in minpq.h **********************//*Creates a new minimizing priority queue.*/struct min_pq* minpq_init(){	struct min_pq* min_pq;	min_pq = malloc( sizeof( struct min_pq ) );	min_pq->pq_array = calloc( MINPQ_INIT_NALLOCD, sizeof( struct pq_node ) );	min_pq->nallocd = MINPQ_INIT_NALLOCD;	min_pq->n = 0;	return min_pq;}/**Inserts an element into a minimizing priority queue.@param min_pq a minimizing priority queue@param data the data to be inserted@param key the key to be associated with \a data@return Returns 0 on success or 1 on failure.*/int minpq_insert( struct min_pq* min_pq, void* data, int key ){	int n = min_pq->n;	/* double array allocation if necessary */	if( min_pq->nallocd == n )	{		min_pq->nallocd = array_double( &min_pq->pq_array, min_pq->nallocd,										sizeof( struct pq_node ) );		if( ! min_pq->nallocd )		{			fprintf( stderr, "Warning: unable to allocate memory, %s, line %d\n",					__FILE__, __LINE__ );			return 1;		}	}	min_pq->pq_array[n].data = data;	min_pq->pq_array[n].key = INT_MAX;	decrease_pq_node_key( min_pq->pq_array, min_pq->n, key );	min_pq->n++;	return 0;}/*Returns the element of a minimizing priority queue with the smallest keywithout removing it from the queue.@param min_pq a minimizing priority queue@return Returns the element of \a min_pq with the smallest key or NULLif \a min_pq is empty*/void* minpq_get_min( struct min_pq* min_pq ){	if( min_pq->n < 1 )	{		fprintf( stderr, "Warning: PQ empty, %s line %d\n", __FILE__, __LINE__ );		return NULL;	}	return min_pq->pq_array[0].data;}/*Removes and returns the element of a minimizing priority queue with thesmallest key.@param min_pq a minimizing priority queue@return Returns the element of \a min_pq with the smallest key of NULLif \a min_pq is empty*/void* minpq_extract_min( struct min_pq* min_pq ){	void* data;	if( min_pq->n < 1 )	{		fprintf( stderr, "Warning: PQ empty, %s line %d\n", __FILE__, __LINE__ );		return NULL;	}	data = min_pq->pq_array[0].data;	min_pq->n--;	min_pq->pq_array[0] = min_pq->pq_array[min_pq->n];	restore_minpq_order( min_pq->pq_array, 0, min_pq->n );	return data;}/*De-allocates the memory held by a minimizing priorioty queue@param min_pq pointer to a minimizing priority queue*/void minpq_release( struct min_pq** min_pq ){	if( ! min_pq )	{		fprintf( stderr, "Warning: NULL pointer error, %s line %d\n", __FILE__,				__LINE__ );		return;	}	if( *min_pq  &&  (*min_pq)->pq_array )	{		free( (*min_pq)->pq_array );		free( *min_pq );		*min_pq = NULL;	}}/************************ Functions prototyped here **************************//*Decrease a minimizing pq element's key, rearranging the pq if necessary@param pq_array minimizing priority queue array@param i index of the element whose key is to be decreased@param key new value of element <EM>i</EM>'s key; if greater than current	key, no action is taken*/void decrease_pq_node_key( struct pq_node* pq_array, int i, int key ){	struct pq_node tmp;	if( key > pq_array[i].key )		return;	pq_array[i].key = key;	while( i > 0  &&  pq_array[i].key < pq_array[parent(i)].key )	{		tmp = pq_array[parent(i)];		pq_array[parent(i)] = pq_array[i];		pq_array[i] = tmp;		i = parent(i);	}}/*Recursively restores correct priority queue order to a minimizing pq array@param pq_array a minimizing priority queue array@param i index at which to start reordering@param n number of elements in \a pq_array*/void restore_minpq_order( struct pq_node* pq_array, int i, int n ){	struct pq_node tmp;	int l, r, min = i;	l = left( i );	r = right( i );	if( l < n )		if( pq_array[l].key < pq_array[i].key )			min = l;	if( r < n )		if( pq_array[r].key < pq_array[min].key )			min = r;	if( min != i )	{		tmp = pq_array[min];		pq_array[min] = pq_array[i];		pq_array[i] = tmp;		restore_minpq_order( pq_array, min, n );	}}