p(247)赫夫曼编码

算法主要在做的事就是从堆中取出两个元素合并成一个新元素，再插入堆中，同时构建二叉树

注意堆中要存下二叉树元素的地址，方便引用

#include<stdio.h>
#include<stdlib.h>
struct node{
int f;
struct node *l,*r;
};
struct heap{
int f;
struct node *hnode;
};
int minheapify(struct heap *q,int i,int heapsize)
{
int min;
struct heap tmp;
tmp=q[i];
while (1)
{
min=i;
if (i*2<=heapsize)
min=tmp.f<q[i*2].f?i:i*2;
if (i*2+1<=heapsize)
min=q[min].f<q[i*2+1].f?min:i*2+1;
if (min!=i)
{
q[i]=q[min];
i=min;
}
else
break;
}
q[min]=tmp;
return 0;
}
int buildminheap(struct heap*q,int heapsize)
{
int i;
for (i=heapsize/2;i>=1;i--)
minheapify(q,i,heapsize);
return 0;
}
struct node * extractmin(struct heap *q,int heapsize)
{
struct heap tmp;
tmp=q[1];
q[1]=q[heapsize];
minheapify(q,1,heapsize-1);
return tmp.hnode;
}
int insert(struct heap *q,struct node *new,int heapsize)
{
struct heap tmp;
int min,i;
heapsize++;
q[heapsize].f=new->f;
q[heapsize].hnode=new;
tmp=q[heapsize];
i=heapsize;
while (1)
{
min=i;
if ((i>1)&&(q[i/2].f>tmp.f))
min=i/2;
if (min!=i)
{
q[i]=q[min];
i=min;
}
else
break;
}
q[min]=tmp;
return 0;
}
struct node * huffman(struct heap *q,int n)
{
int i;
struct node *new;
for (i=n;i>1;i--)//heapsize
{
new=(struct node *)malloc(sizeof(struct node));
new->l=extractmin(q,i);
new->r=extractmin(q,i-1);
new->f=new->l->f+new->r->f;
insert(q,new,i-2);
}
return new;
}
int print(struct node *root)
{
if (root==NULL)
{
printf("# ");
return 0;
}
printf("%d ",root->f);
print(root->l);
print(root->r);
return 0;
}
int main(void)
{
int n,i;
struct heap* q;
scanf("%d",&n);
q=(struct heap *)malloc(sizeof(struct heap)*(n+1));
for (i=1;i<=n;i++)
{
q[i].hnode=(struct node *)malloc(sizeof(struct node));
q[i].hnode->l=NULL;
q[i].hnode->r=NULL;
scanf("%d",&q[i].f);
q[i].hnode->f=q[i].f;
}
buildminheap(q,n);
struct node *hroot;
hroot=huffman(q,n);
print(hroot);
return 0;
}