Geografic-Information-System/vector/v.voronoi/sw_heap.c

#include <stdlib.h>
#include "sw_defs.h"


int PQinsert(struct Halfedge *he, struct Site *v, double offset)
{
    struct Halfedge *last, *next;

    he->vertex = v;
    ref(v);
    he->ystar = v->coord.y + offset;
    last = &PQhash[PQbucket(he)];
    while ((next = last->PQnext) != (struct Halfedge *)NULL &&
	   (he->ystar > next->ystar ||
	    (he->ystar == next->ystar && v->coord.x > next->vertex->coord.x)))
    {
	last = next;
    };
    he->PQnext = last->PQnext;
    last->PQnext = he;
    PQcount += 1;
    return 0;
}

int PQdelete(struct Halfedge *he)
{
    struct Halfedge *last;

    if (he->vertex != (struct Site *)NULL) {
	last = &PQhash[PQbucket(he)];
	while (last->PQnext != he)
	    last = last->PQnext;
	last->PQnext = he->PQnext;
	PQcount -= 1;
	deref(he->vertex);
	he->vertex = (struct Site *)NULL;
    };
    return 0;
}

int PQbucket(struct Halfedge *he)
{
    int bucket;

    bucket = (he->ystar - ymin) / deltay * PQhashsize;
    if (bucket < 0)
	bucket = 0;
    if (bucket >= PQhashsize)
	bucket = PQhashsize - 1;
    if (bucket < PQmin)
	PQmin = bucket;
    return (bucket);
}



int PQempty(void)
{
    return (PQcount == 0);
}


struct Point PQ_min(void)
{
    struct Point answer;

    while (PQhash[PQmin].PQnext == (struct Halfedge *)NULL) {
	PQmin += 1;
    };
    answer.x = PQhash[PQmin].PQnext->vertex->coord.x;
    answer.y = PQhash[PQmin].PQnext->ystar;
    return (answer);
}

struct Halfedge *PQextractmin(void)
{
    struct Halfedge *curr;

    curr = PQhash[PQmin].PQnext;
    PQhash[PQmin].PQnext = curr->PQnext;
    PQcount -= 1;
    return (curr);
}


int PQinitialize(void)
{
    int i;

    PQcount = 0;
    PQmin = 0;
    PQhashsize = 4 * sqrt_nsites;
    PQhash = (struct Halfedge *)myalloc(PQhashsize * sizeof *PQhash);
    for (i = 0; i < PQhashsize; i += 1)
	PQhash[i].PQnext = (struct Halfedge *)NULL;

    return 0;
}