用c语言写哈夫曼树的文件压缩

下面是使用C语言实现哈夫曼树进行文件压缩的示例代码：

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

#define MAX_TREE_HT 100

// 定义哈夫曼树结点
struct MinHeapNode {
    char data;
    unsigned freq;
    struct MinHeapNode *left, *right;
};

// 定义哈夫曼树
struct MinHeap {
    unsigned size;
    unsigned capacity;
    struct MinHeapNode **array;
};

// 创建一个新的哈夫曼树结点
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;
}

// 创建一个空的哈夫曼树
struct MinHeap *createMinHeap(unsigned capacity) {
    struct MinHeap *minHeap = (struct MinHeap*)malloc(sizeof(struct MinHeap));
    minHeap->size = 0;
    minHeap->capacity = capacity;
    minHeap->array = (struct MinHeapNode**)malloc(minHeap->capacity * sizeof(struct MinHeapNode*));
    return minHeap;
}

// 交换两个哈夫曼树结点
void swapMinHeapNode(struct MinHeapNode** a, struct MinHeapNode** b) {
    struct MinHeapNode* t = *a;
    *a = *b;
    *b = t;
}

// 维护最小堆的性质
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);
    }
}

// 判断最小堆是否只有一个结点
int isSizeOne(struct MinHeap* minHeap) {
    return (minHeap->size == 1);
}

// 从最小堆中取出最小的结点
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;
}

// 插入一个结点到最小堆中
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;
}

// 判断是否为叶子结点
int isLeaf(struct MinHeapNode* root) {
    return !(root->left) && !(root->right);
}

// 创建一个最小堆并构建哈夫曼树
struct MinHeap* createAndBuildMinHeap(char data[], int freq[], int size) {
    struct MinHeap* minHeap = createMinHeap(size);
    for (int i = 0; i < size; ++i)
        minHeap->array[i] = newNode(data[i], freq[i]);
    minHeap->size = size;

    while (!isSizeOne(minHeap)) {
        struct MinHeapNode *left = extractMin(minHeap);
        struct MinHeapNode *right = extractMin(minHeap);

        struct MinHeapNode *top = newNode('$', left->freq + right->freq);
        top->left = left;
        top->right = right;
        insertMinHeap(minHeap, top);
    }

    return extractMin(minHeap);
}

// 打印哈夫曼编码
void printCodes(struct MinHeapNode* root, int arr[], int top, FILE *fp) {
    // 遍历到叶子结点
    if (root->left) {
        arr[top] = 0;
        printCodes(root->left, arr, top + 1, fp);
    }

    if (root->right) {
        arr[top] = 1;
        printCodes(root->right, arr, top + 1, fp);
    }

    if (isLeaf(root)) {
        fprintf(fp, "%c:", root->data);
        for (int i = 0; i < top; ++i) {
            fprintf(fp, "%d", arr[i]);
        }
        fprintf(fp, "\n");
    }
}

// 压缩文件
void compressFile(char* fileName, FILE *fp) {
    int freq[256] = {0};
    char data[256];

    // 统计字符出现频率
    int ch;
    while ((ch = fgetc(fp)) != EOF) {
        ++freq[ch];
    }

    int size = 0;
    for (int i = 0; i < 256; ++i) {
        if (freq[i] != 0) {
            data[size++] = (char)i;
        }
    }

    // 构建哈夫曼树
    struct MinHeapNode* root = createAndBuildMinHeap(data, freq, size);

    int arr[MAX_TREE_HT], top = 0;
    printCodes(root, arr, top, stdout);
}

int main() {
    char fileName[] = "test.txt";
    FILE *fp = fopen(fileName, "r");

    if (fp == NULL) {
        printf("Error opening file\n");
        exit(1);
    }

    compressFile(fileName, fp);

    fclose(fp);
    return 0;
}

这段代码实现了从文件中读取数据，统计字符出现频率，构建哈夫曼树，生成哈夫曼编码，以及输出哈夫曼编码。这个示例仅仅是生成了哈夫曼编码，还需要将原始文本进行编码压缩，这个可以参考哈夫曼编码的实现来完成。