```
#include <stdio.h>
#include <stdarg.h>
#define MAX_HEAP_SIZE 1000
#define PARENT(i) (i/2) // given the index of a heap node, the returns the parent index
#define LEFT(i) (2*i) // given the index of a heap node, the returns the left child index
#define RIGHT(i) (2*i + 1) // given the index of a heap node, the returns the right child index
#define SWAP(a, b, temp) {temp=a; a=b; b=temp;}
typedef struct {
void *a[MAX_HEAP_SIZE];
int size;
} heap;
void heap_init(heap *h);
void heapify(heap *h, int (*comp_func)(void*, void*), int i);
void build_heap(heap *h, int (*comp_func)(void*, void*));
void* heap_extract_max(heap *h, int (*comp_func)(void*, void*));
void heap_insert(heap *h, int (*comp_func)(void*, void*), void *key);
// set heap size to 0 and NULL out all values
void heap_init(heap *h)
{
int j;
h->size = 0;
for(j = 0; j < MAX_HEAP_SIZE; j++)
h->a[j] = NULL;
return;
}
// Adapted from Introduction to Algorithms, 1990,
// by Cormen, Leiserson, Rivest, and Stein.
// Chapter 7, Section 7.2
void heapify(heap *h, int (*comp_func)(void*, void*), int i)
{
void *temp = NULL;
int largest,
l = LEFT(i),
r = RIGHT(i);
if(l <= h->size && comp_func(h->a[l], h->a[i]) > 0)
largest = l;
else
largest = i;
if(r <= h->size && comp_func(h->a[r], h->a[largest]) > 0)
largest = r;
if(largest != i) {
SWAP(h->a[i], h->a[largest], temp);
heapify(h, comp_func, largest);
}
return;
}
// Adapted from Introduction to Algorithms, 1990,
// by Cormen, Leiserson, Rivest, and Stein.
// Chapter 7, Section 7.3
void build_heap(heap *h, int (*comp_func)(void*, void*))
{
int i;
for(i = h->size/2; i > 0; i--)
heapify(h, comp_func, i);
return;
}
// Adapted from Introduction to Algorithms, 1990,
// by Cormen, Leiserson, Rivest, and Stein.
// Chapter 7, Section 7.5
void* heap_extract_max(heap *h, int (*comp_func)(void*, void*))
{
if(h->size < 1)
return NULL;
void *max = h->a[1],
*temp = NULL;
SWAP(h->a[1], h->a[h->size], temp);
h->size--;
heapify(h, comp_func, 1);
return max;
}
// Adapted from Introduction to Algorithms, 1990,
// by Cormen, Leiserson, Rivest, and Stein.
// Chapter 7, Section 7.5
void heap_insert(heap *h, int (*comp_func)(void*, void*), void *key)
{
int i = ++h->size;
while(i > 1 && comp_func(h->a[PARENT(i)], key) < 0) {
h->a[i] = h->a[PARENT(i)];
i = PARENT(i);
}
h->a[i] = key;
return;
}```请解释这段代码的作用
本文介绍了一种使用二分法解决H指数问题的方法。H指数是指一位科研人员迄今为止发表的所有论文中，有H篇论文分别被引用了至少H次，其余论文每篇被引用次数不多于H次。该算法首先对引用次数进行排序，然后通过二分查找确定最大的H指数。
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