//哈弗曼編碼的演算法
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define N 50//葉子結點的最大值
#define M 2*N-1  //所有結點的最大值
typedef struct
{
    int weight;
    int parent;
    int LChild;
    int RChild;
} HTNode,HuffmanTree[M+1];

void select(HuffmanTree ht,int n,int *s1,int *s2)  //找權值最小的兩個結點
{
    int i;
    int minn=999999;
    int lable1=0,lable2=0;
    for(i=1;i<=n;i++)
    {
        if(ht[i].parent==0 && ht[i].weight<minn)
        {
            minn=ht[i].weight;
            lable1=i;
        }
    }
    *s1=lable1;
    minn=999999;
    for( i=1;i<=n;i++)
    {
        if(ht[i].parent==0 && ht[i].weight<minn && lable1 != i)
        {
            minn=ht[i].weight;
            lable2=i;
        }
    }
    *s2=lable2;
}

void CrtHuffmanTree(HuffmanTree ht,int w[],int n) //建立哈夫曼樹  w[]裡面存放n個結點的權值
{
    int i;
    for(i=1;i<=n;i++)
    {
        ht[i].weight=w[i];
        ht[i].LChild=0;
        ht[i].RChild=0;
        ht[i].parent=0;
    }
    int m=2*n-1;
    for(i=n+1;i<=m;i++)
    {
        ht[i].weight=0;
        ht[i].LChild=0;
        ht[i].RChild=0;
        ht[i].parent=0;

    }
    int s1,s2;
    for(i=n+1;i<=m;i++)
    {
        select(ht,i-1,&s1,&s2);
        ht[i].weight=ht[s1].weight+ht[s2].weight;
        ht[s1].parent=i;
        ht[s2].parent=i;
        ht[i].LChild=s1;
        ht[i].RChild=s2;
    }
}

void CrtHuffmanCode(HuffmanTree ht,int n )
{
    char cd[n+1][n+1] ;
    int i;int start;

    for(i=1;i<=n;i++)
    {
        cd[i][n-1]='\0';   //從右向左存放編碼
        start=n-1;
        int c=i; int p=ht[i].parent;
        while(p!=0)
        {
            --start;
            if(ht[p].LChild==c) cd[i][start]='0';
                else cd[i][start]='1';
            c=p;
            p=ht[p].parent;
        }
        int j;
        for(j=start;cd[i][j]!='\0';j++)
            printf("%c",cd[i][j]);
        printf("\n");
    }
    return ;
}

int main()
{
    int n,i,leaf;
    int w[1000];
    HuffmanTree ht;
    printf("請輸入葉子結點的個數n 以及其權值\n");
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        scanf("%d",&leaf);
        w[i]=leaf;
    }
     CrtHuffmanTree(ht,w,n);
     printf("構造的哈夫曼樹的結構為：\n");
    for(i=1;i<=2*n-1;i++)
    {
        printf("%d %d %d %d\n",ht[i].weight,ht[i].parent,ht[i].LChild,ht[i].RChild);

    }
    printf("哈夫曼樹的編碼為：\n");
    CrtHuffmanCode(ht,n);

    return 0;
}