【数据结构】Huffman树

参照书上写的Huffman树的代码 结构用的是线性存储的结构 不是二叉链表 里面要用到查找最小和第二小 理论上锦标赛法比较好 但是实现好麻烦啊 考虑到数据量不是很大 就直接用比较笨的先找最小 去掉最小再找第二小的方法了。

#include <stdio.h>

#include <stdlib.h>

#include <string.h>



typedef struct{

    unsigned int weight;

    unsigned int parent, lchild, rchild;

}HTNode, *HuffmanTree;



typedef char ** HuffmanCode;



int Select(HuffmanTree HT, int n, int &s1, int &s2)

{

    if(n <= 1) return 1;

    else

    {

        int i;

        s1 = 0; s2 = 0;

        for(i = 1; i <= n; i++)

        {

            if(s1 == 0 && HT[i].parent == 0)

            {

                s1 = i;

            }

            else if(HT[i].parent == 0 && HT[i].weight < HT[s1].weight && s1 != 0)

            {

                s1 = i;

            }

        }

        for(i = 1; i <= n; i++)

        {

            if(i == s1)

            {

                continue;

            }

            else if(s2 == 0 && HT[i].parent == 0)

            {

                s2 = i;

            }

            else if(HT[i].parent == 0 && HT[i].weight < HT[s2].weight && s2 != 0)

            {

                s2 = i;

            }

        }

    }

    return 0;

}

void HuffmanCoding(HuffmanTree &HT, HuffmanCode &HC, int * w, int n)

{

    if(n <= 1) return;

    int m = 2 * n - 1;

    HuffmanTree p;

    int i;

    HT = (HuffmanTree)malloc((m + 1) * sizeof(HTNode));

    for(p = HT, i = 1; i <= n; i++, p++, w++)  //初始化

    {

        p->weight = *w; p->parent = 0; p->rchild = 0; p->lchild = 0;

    }

    for( ; i <= m; i++, p++)

    {

        p->weight = 0; p->parent = 0; p->rchild = 0; p->lchild = 0;

    }



    for(i = n + 1; i <= m; i++) //建Huffman树

    {

        int s1, s2;

        Select(HT, i - 1, s1, s2);

        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;

        HT[i].parent = 0; //不加这句会出错

    }



    HC = (HuffmanCode)malloc((n + 1) * sizeof(char *));

    char * cd = (char *)malloc(n * sizeof(char));

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

    for(i = 1; i <= n; i++)

    {

        int start = n - 1;

        int c, f;

        for(c = i, f = HT[i].parent; f != 0; c = f, f = HT[f].parent)

        {

            if(HT[f].lchild == c) cd[--start] = '0';

            else{ cd[--start] = '1';}

        }

        HC[i] = (char *)malloc((n - start) * sizeof(char));

        strcpy(HC[i], &cd[start]);

    }

    free(cd);

}



int main()

{

    int N = 10; //一共10个权值

    int w[10] = {1,2,3,4,5,6,7,8,9,0};

    HuffmanTree HT;

    HuffmanCode HC;

    HuffmanCoding(HT, HC,  w, N);



    int i, j;

    for(i = 1; i <= N; i++)

    {

        printf("%d: ", i);

        for(j = 0; HC[i][j] != '\0'; j++)

        {

            printf("%c", HC[i][j]);

        }

        printf("\n");

    }



    return 0;

}