c语言实现哈夫曼编码

迈不过友情╰ 2024-02-19 12:00 45阅读 0赞

要实现哈夫曼编码，需要以下步骤：

1.  统计字符出现的频率
2.  构建哈夫曼树
3.  遍历哈夫曼树，给不同的字符赋予不同的编码
4.  将编码后的字符写入文件中

下面是一个简单的 C 语言实现：

#include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    #define MAX_TREE_HT 100
    
    // 节点结构体
    struct MinHeapNode {
        char data; // 字符
        unsigned freq; // 频率
        struct MinHeapNode *left, *right; // 左右子节点
    };
    
    // 哈夫曼树结构体
    struct MinHeap {
        unsigned size; // 大小
        unsigned capacity; // 容量
        struct MinHeapNode** array; // 数组
    };
    
    // 创建节点
    struct MinHeapNode* newNode(char data, unsigned freq) {
        struct MinHeapNode* temp = (struct MinHeapNode*) malloc(sizeof(struct MinHeapNode));
        temp->left = temp->right = NULL;
        temp->data = data;
        temp->freq = freq;
        return temp;
    }
    
    // 创建一个大小为 capacity 的空的 MinHeap
    struct MinHeap* createMinHeap(unsigned capacity) {
        struct MinHeap* minHeap = (struct MinHeap*) malloc(sizeof(struct MinHeap));
        minHeap->size = 0; // 初始化大小为 0
        minHeap->capacity = capacity;
        minHeap->array = (struct MinHeapNode**)malloc(minHeap->capacity * sizeof(struct MinHeapNode));
        return minHeap;
    }
    
    // 交换 *a 和 *b 的值
    void swapMinHeapNode(struct MinHeapNode** a, struct MinHeapNode** b) {
        struct MinHeapNode* temp = *a;
        *a = *b;
        *b = temp;
    }
    
    // 维护最小堆的特性
    void minHeapify(struct MinHeap* minHeap, int idx) {
        int smallest = idx;
        int left = 2 * idx + 1;
        int right = 2 * idx + 2;
      
        if (left < minHeap->size && minHeap->array[left]->freq < minHeap->array[smallest]->freq)
            smallest = left;
      
        if (right < minHeap->size && minHeap->array[right]->freq < minHeap->array[smallest]->freq)
            smallest = right;
      
        if (smallest != idx) {
            swapMinHeapNode(&minHeap->array[smallest], &minHeap->array[idx]);
            minHeapify(minHeap, smallest);
        }
    }
    
    // 检查大小为 1 的最小堆
    int isSizeOne(struct MinHeap* minHeap) {
        return (minHeap->size == 1);
    }
    
    // 从 MinHeap 中取出最小的节点 (最小堆的根)
    struct MinHeapNode* extractMin(struct MinHeap* minHeap) {
        struct MinHeapNode* temp = minHeap->array[0];
        minHeap->array[0] = minHeap->array[minHeap->size - 1];
        --minHeap->size;
        minHeapify(minHeap, 0);
        return temp;
    }
    
    // 插入新的节点到 MinHeap 中
    void insertMinHeap(struct MinHeap* minHeap, struct MinHeapNode* minHeapNode) {
        ++minHeap->size;
        int i = minHeap->size - 1;
      
        while (i && minHeapNode->freq < minHeap->array[(i - 1) / 2]->freq) {
            minHeap->array[i] = minHeap->array[(i - 1) / 2];
            i = (i - 1) / 2;
        }
    
        minHeap->array[i] = minHeapNode;
    }
    
    // 判断当前节点是否是叶子节点
    int isLeaf(struct MinHeapNode* root) {
        return !(root->left) && !(root->right);
    }
    
    // 创建并构建哈夫曼树
    struct MinHeapNode* buildHuffmanTree(char data[], int freq[], int size) {
        struct MinHeapNode *left, *right, *top;
      
        // 创建一个最小堆，并初始化大小
        struct MinHeap* minHeap = createMinHeap(size);
        for (int i = 0; i < size; ++i)
            minHeap->array[i] = newNode(data[i], freq[i]);
        minHeap->size