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#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include "util.h"
typedef int T;
// https://stackoverflow.com/a/22900767
#define LEFT(idx) (idx*2+1)
#define RIGHT(idx) (idx*2+2)
#define PARENT(idx) ((idx-1)/2)
static void
swap(T heap[], int i, int j)
{
T temp = heap[i];
heap[i] = heap[j];
heap[j] = temp;
}
static void
fixup(T heap[], int i)
{
int p = PARENT(i);
while ( i > 0 && heap[p] < heap[i] ) {
swap(heap, i, p);
i = p;
p = PARENT(i);
}
}
static void
fixdown(T heap[], int i, int n)
{
for ( ;; ) {
const int l = LEFT(i);
const int r = RIGHT(i);
int m = i;
if ( l < n && heap[m] < heap[l] )
m = l;
if ( r < n && heap[m] < heap[r] )
m = r;
if ( m == i )
break;
swap(heap, m, i);
i = m;
}
}
static void
heapify(T heap[], int n)
{
for ( int i = n / 2 - 1; i >= 0; --i )
fixdown(heap, i, n);
}
static void
my_heapsort(T a[], int n)
{
heapify(a, n);
for ( int i = n - 1; i >= 0; --i ) {
swap(a, 0, i);
fixdown(a, 0, i);
}
}
// -------------------------------------------
struct pq { // Priority Queue
T heap[251];
int sz;
};
void
pq_init(struct pq *pq)
{
pq->sz = 0;
}
bool
pq_push(struct pq *pq, T data)
{
if ( pq->sz == NELEM(pq->heap) )
return false;
pq->heap[pq->sz] = data;
fixup(pq->heap, pq->sz);
++pq->sz;
return true;
}
bool
pq_pop(struct pq *pq, T* data)
{
if ( pq->sz == 0 )
return false;
*data = pq->heap[0];
--pq->sz;
pq->heap[0] = pq->heap[pq->sz];
fixdown(pq->heap, 0, pq->sz);
return true;
}
// -------------------------------------------
void print_heap(T heap[], int n)
{
if ( n ) {
printf("%d", heap[0]);
for ( int i = 1; i != n; ++i )
printf(", %d", heap[i]);
putchar('\n');
}
}
int main(void)
{
#if 0 // Heap-Testprogramm
T heap[20] = { 18, 18, 16, 9, 7, 1, 9, 3, 7, 5 };
print_heap(heap, 10);
//heap[10] = 13; fixup(heap, 10);
swap(heap, 0, 9); fixdown(heap, 0, 9);
print_heap(heap, 9);
#endif
struct pq pq[1];
pq_init(pq);
for ( int i = 0; i != 10; ++i )
pq_push(pq, rand());
T data;
while ( pq_pop(pq, &data) )
printf("%d\n", data);
}
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