// HuffmanTree.cpp : 定義控制檯應用程式的入口點。

 #include "stdafx.h"
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>

 typedef struct HuffmanTree
 {
   int weight;
   int parent, lchild, rchild;
 } HuffmanTree;

 typedef struct CodeNode
 {
   int ch;
   char bits[4+1];
 }CodeNode;

 void SelectMin(HuffmanTree tree[], int len, int * pos1, int* pos2)
 {
   int min=255;
   int i, j;
   *pos1=0;
   *pos2=0;
   for(i=0; i<len; i++)
   {
     if(tree[i].parent==-1)
       if(min>tree[i].weight)
       {
         min=tree[i].weight;
         *pos1=i;
       }
   }
   min=255;

   for(j=0; j<len; j++)
   {
     if(j==*pos1)
       continue;
     if(tree[j].parent==-1)
       if(min>tree[j].weight)
       {
         min=tree[j].weight;
         *pos2=j;
       }
   }
 }

 void CreateHuffmanTree(HuffmanTree tree[], int n)
 {
   int m=2*n;
   int i;
   for(i=n; i<m-1; i++)
   {
     int pos1, pos2;
     HuffmanTree node;
     SelectMin(tree, i, &pos1, &pos2);
     printf("pos1=%d,pos2=%d\n", pos1, pos2);
     node.weight=tree[pos1].weight+tree[pos2].weight;
     tree[pos1].parent=i;
     tree[pos2].parent=i;
     node.lchild=pos1;
     node.rchild=pos2;
     node.parent=-1;
     tree[i]=node;
   }
 }

 void HuffmanEncoding(HuffmanTree tree[])
 {
   int c, p, i;
   int start;
   char cd[4+1];
   cd[4]='\0';

   for(i=0; i<4; i++)
   {
     printf("\n");
     printf("%d",tree[i].weight);
     printf(":");
     start=4;
     c=i;
     while((p=tree[c].parent)!=-1)
     {
       if(tree[p].lchild==c)
       {
         cd[--start]='0';
       }
       else
       {
         cd[--start]='1';
       }
       c=p;
     }
     printf(&cd[start]);
   }
 }

 int main(int argc, char* argv[])
 {
   HuffmanTree tree[4*2];
   int i, j;
   for(i=0; i<4; i++)
   {
     tree[i].lchild=-1;
     tree[i].rchild=-1;
	 tree[i].parent=-1;
   }

   printf("請輸入哈夫曼樹葉子結點的權值: \n");
   for(i=0; i<4; i++)     //讀入葉子結點的權值
   {
     int weight;
     scanf("%d",&weight);
     tree[i].weight=weight;
   }

   CreateHuffmanTree(tree, 4);
   for(j=0; j<2*4-1; j++)
   {
      printf("tree[%d]:weight=%d \n", j, tree[j].weight);
   }

   HuffmanEncoding(tree);
   
   return 0;
 }