哈夫曼树（数组表示）仅代码

关于哈夫曼树的介绍，网上的资料很多，这里就不多介绍了。下面是C语言的代码实现。GCC5.3.0编译通过。

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// Created by Jacky on 2017-5-18 // main.c -- 哈夫曼树（数组表示）   #include <stdio.h> #include <stdlib.h>   /**  * 哈夫曼树的结点定义  */ typedef struct HuffmanNode {     char data;  // 字符     int weight; // 权值，字符出现次数     int parent; // 父结点的数组下标     int left;   // 左孩子的数组下标     int right;  // 右孩子的数组下标 } HuffmanNode;   /**  * 哈夫曼树定义  */ typedef struct HuffmanTree {     int count;          // 结点数，也就是数组长度 = 2 * 叶子结点 - 1     HuffmanNode *nodes; // 结点数组 } HuffmanTree;   #define HUFFMANTREE_INIT {0, NULL}   void InitHuffmanTree(HuffmanTree *T, const char *str); void CreateHuffmanTree(HuffmanTree *T); void PrintHuffmanTree(HuffmanTree T); void Visit(HuffmanNode *node); void PreOrderTraversal(HuffmanTree T, void (*visit)(HuffmanNode *)); void InOrderTraversal(HuffmanTree T, void (*visit)(HuffmanNode *)); void PostOrderTraversal(HuffmanTree T, void (*visit)(HuffmanNode *));   int main(int argc, char const *argv[]) {     HuffmanTree T = HUFFMANTREE_INIT;     InitHuffmanTree(&T, "aaaabbc");     CreateHuffmanTree(&T);     PrintHuffmanTree(T);     // PostOrderTraversal(T, Visit);       free(T.nodes);// 释放结点申请的内存     T.nodes = NULL;     return 0; }   /**  * 初始化哈夫曼树。  * 根据给定的字符串，统计每个字符出现的次数。  * 并用统计的信息来构造哈夫曼树的叶子结点。  * @param T   哈夫曼树对象指针  * @param str 需要统计的字符串  */ void InitHuffmanTree(HuffmanTree *T, const char *str) {     // 统计每个字符出现的次数。     int arr[256] = {0};     while (*str)     {         arr[*str]++;         str++;     }       int leafCount = 0;       // 统计叶子结点的个数。     for (int i = 0; i < sizeof(arr) / sizeof(arr[0]); ++i)     {         if (arr[i])         {             leafCount++;             // printf("%c %d\n", i, arr[i]);         }     }       // printf("leafCount = %d.\n", leafCount);       HuffmanNode *nodes = (HuffmanNode *)malloc((2 * leafCount - 1) * sizeof(HuffmanNode));     T->count = 2 * leafCount - 1;       leafCount = 0;     for (int i = 0; i < sizeof(arr) / sizeof(arr[0]); ++i)     {         if (arr[i])         {             nodes[leafCount].data = i;             nodes[leafCount].weight = arr[i];             nodes[leafCount].parent = nodes[leafCount].left = nodes[leafCount].right = -1;             leafCount++;         }     }     T->nodes = nodes; }   /**  * 通过给定的叶子结点构造整棵哈夫曼树。  * @param T 哈夫曼树对象指针  */ void CreateHuffmanTree(HuffmanTree *T) {     int leafCount = (T->count + 1) / 2;// 结点数 = 2 * 叶子结点 - 1       for (int i = leafCount; i < T->count; ++i)     {         int min1 = -1;// weight最小的结点数组下标         int min2 = -1;// weight次小的结点数组下标         for (int j = 0; j < i; ++j)         {             if (T->nodes[j].parent == -1)             {                 if (min1 == -1)// 第一次进入的时候，给min1赋值                 {                     min1 = j;                 }                 else if (min2 == -1)// 第二次进入的时候，给min1，min2赋值                 {                     if (T->nodes[j].weight < T->nodes[min1].weight)                     {                         min2 = min1;                         min1 = j;                     }                     else                     {                         min2 = j;                     }                 }                 else// 第三次及之后进入                 {                     if (T->nodes[j].weight < T->nodes[min1].weight)                     {                         min2 = min1;                         min1 = j;                     }                     else if (T->nodes[j].weight < T->nodes[min2].weight)                     {                         min2 = j;                     }                 }             }         }         // printf("min1 = %d, min2 = %d.\n", min1, min2);         T->nodes[i].data = 0;         T->nodes[i].weight = T->nodes[min1].weight + T->nodes[min2].weight;         T->nodes[i].parent = -1;         T->nodes[i].left = min1;         T->nodes[i].right = min2;           T->nodes[min1].parent = T->nodes[min2].parent = i;     } }   /**  * 哈夫曼树的结点的访问  * @param node 结点地址  */ void Visit(HuffmanNode *node) {     printf("%c %2d\n", node->data, node->weight); }   void PreOrder(HuffmanTree T, void (*visit)(HuffmanNode *), int index) {     if (index != -1)     {         visit(&T.nodes[index]);         PreOrder(T, visit, T.nodes[index].left);         PreOrder(T, visit, T.nodes[index].right);     } }   void InOrder(HuffmanTree T, void (*visit)(HuffmanNode *), int index) {     if (index != -1)     {         InOrder(T, visit, T.nodes[index].left);         visit(&T.nodes[index]);         InOrder(T, visit, T.nodes[index].right);     } }   void PostOrder(HuffmanTree T, void (*visit)(HuffmanNode *), int index) {     if (index != -1)     {         PostOrder(T, visit, T.nodes[index].left);         visit(&T.nodes[index]);         PostOrder(T, visit, T.nodes[index].right);     } }   /**  * 前序遍历  */ void PreOrderTraversal(HuffmanTree T, void (*visit)(HuffmanNode *)) {     PreOrder(T, visit, T.count - 1); }   /**  * 中序遍历  */ void InOrderTraversal(HuffmanTree T, void (*visit)(HuffmanNode *)) {     InOrder(T, visit, T.count - 1); }   /**  * 后续遍历  */ void PostOrderTraversal(HuffmanTree T, void (*visit)(HuffmanNode *)) {     PostOrder(T, visit, T.count - 1); }   /**  * 打印哈夫曼树信息，方便调试  * @param T         哈夫曼树对象  */ void PrintHuffmanTree(HuffmanTree T) {     printf("\ncount = %d.\n", T.count);     char *rows[] = {"index", "data", "weight", "parent", "left", "right"};     int count = T.count;       for (int i = 0; i < sizeof(rows) / sizeof(rows[0]); ++i)     {         if (i == 0)         {             printf("+--------+");             for (int i = 0; i < count; ++i)             {                 printf("----+");             }         }         printf("\n|%-8s|", rows[i]);         for (int j = 0; j < count; ++j)         {             switch (i)             {             case 0:// index                 printf(" %-3d|", j);                 break;             case 1:// data                 if (T.nodes[j].data == 10)// 回车                 {                     printf(" %-3d|", T.nodes[j].data);                 }                 else                 {                     printf(" %-3c|", T.nodes[j].data);                 }                 break;             case 2:// weight                 printf(" %-3d|", T.nodes[j].weight);                 break;             case 3:// parent                 printf(" %-3d|", T.nodes[j].parent);                 break;             case 4:// left                 printf(" %-3d|", T.nodes[j].left);                 break;             case 5:// right                 printf(" %-3d|", T.nodes[j].right);                 break;             }         }         printf("\n+--------+");         for (int j = 0; j < count; ++j)         {             printf("----+");         }     }       printf("\n"); }