树问题总结之哈夫曼树

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
#define N 10         // 带编码字符的个数，即树中叶结点的最大个数
#define M (2*N-1)    // 树中总的结点数目

struct HTNode{        // 树中结点的结构
	unsigned int weight;
	unsigned int parent,lchild,rchild;
};                    
struct HTCode{
	char data;      // 待编码的字符
	int weight;     // 字符的权值
	char code[N];   // 字符的编码
};
void Init(HTCode hc[], int *n){
// 初始化，读入待编码字符的个数n，从键盘输入n个字符和n个权值
	int i;
	printf("input n = ");
	scanf("%d",n);
	getchar();//这里一定要注意啊，处理掉缓冲区的'\n'
		printf("\ninput %d character\n",*n);
	for(i=1; i<=*n; ++i)
		scanf("%c",&hc[i].data);

	printf("\ninput %d weight\n",*n);
	
	for(i=1; i<=*n; ++i)
		scanf("%d",&(hc[i].weight) );
}//
void Select(HTNode ht[], int k, int *s1, int *s2){
// ht[1...k]中选择parent为0，并且weight最小的两个结点，其序号由指针变量s1，s2指示
	
	int i;
	for(i=1; i<=k && ht[i].parent != 0; ++i){ 
		; ;
	}
	*s1 = i;
	for(i=1; i<=k; ++i){
		if(ht[i].parent==0 && ht[i].weight<=ht[*s1].weight)//注意这里面的<=号，为什么要加=呢?先自己思考下吧
			*s1 = i;
	}
	for(i=1; i<=k; ++i){
		if(ht[i].parent==0 && i!=*s1)
		{*s2 = i;break;}
	}
	for(i=1; i<=k; ++i){
		if(ht[i].parent==0 && i!=*s1 && ht[i].weight<=ht[*s2].weight)//同上
			*s2 = i;
	}
}
void HuffmanCoding(HTNode ht[],HTCode hc[],int n){
// 构造Huffman树ht，并求出n个字符的编码
	char cd[N];
	int i,m,c,f,s1,s2,start;
	m = 2*n-1;
	
	for(i=1; i<=m; ++i){
		if(i <= n)
			ht[i].weight = hc[i].weight;
		else
			ht[i].weight = 0;
		ht[i].parent = ht[i].lchild = ht[i].rchild = 0;
	}

	for(i=n+1; i<=m; ++i){
		Select(ht, i-1, &s1, &s2);
		printf("s1位置对应权值：%d    s2位置对应权值：%d\n",ht[s1].weight,ht[s2].weight);//为了看得明白才添加的，
		ht[s1].parent = i;
		ht[s2].parent = i;
		ht[i].lchild = s1;
		ht[i].rchild = s2;
		ht[i].weight = ht[s1].weight+ht[s2].weight;
		printf("新生成节点在ht结构数组中的下标：%d     权值：%d\n",i,ht[i].weight);//同上
		cout<<endl<<endl;
	}

	cd[n-1] = '\0';

	for(i=1; i<=n; ++i){
		start = n-1;
		for(c=i,f=ht[i].parent; f; c=f,f=ht[f].parent){
			if(ht[f].lchild == c)
				cd[--start] = '0';
			else
				cd[--start] = '1';
		}
		strcpy(hc[i].code, &cd[start]);
	}
}
int main()
{
	int i,n;
	HTNode ht[M+1];
	HTCode hc[N+1];
	Init(hc, &n);     // 初始化
 	HuffmanCoding(ht,hc,n);   // 构造Huffman树，并形成字符的编码
	for(i=1; i<=n; ++i)  
		printf("\n%c---%s",hc[i].data,hc[i].code);  
	printf("\n");
	return 0;
}