对一个给定的文本文件，对其进行哈夫曼编码，并计算压缩率。C语言代码

以下是一个简单的C语言代码实现：

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

#define MAX_TREE_HT 100

// 结点结构体
struct MinHeapNode {
    char data;
    unsigned freq;
    struct MinHeapNode *left, *right;
};

// 最小堆结构体
struct MinHeap {
    unsigned size;
    unsigned capacity;
    struct MinHeapNode** array;
};

// 创建新的结点
struct MinHeapNode* newNode(char data, unsigned freq) {
    struct MinHeapNode* node = (struct MinHeapNode*) malloc(sizeof(struct MinHeapNode));
    node->left = node->right = NULL;
    node->data = data;
    node->freq = freq;
    return node;
}

// 创建最小堆
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;
}

// 交换两个结点
void swapMinHeapNode(struct MinHeapNode** a, struct MinHeapNode** b) {
    struct MinHeapNode* t = *a;
    *a = *b;
    *b = t;
}

// 最小堆的堆化
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);
    }
}

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

// 创建最小堆，并插入结点
struct MinHeap* buildMinHeap(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;

    for (int i = (minHeap->size - 1) / 2; i >= 0; --i)
        minHeapify(minHeap, i);

    return minHeap;
}

// 构建哈夫曼树
struct MinHeapNode* buildHuffmanTree(char data[], int freq[], int size) {
    struct MinHeapNode *left, *right, *top;
    struct MinHeap* minHeap = buildMinHeap(data, freq, size);

    while (minHeap->size != 1) {
        left = minHeap->array[0];
        right = minHeap->array[1];

        top = newNode('$', left->freq + right->freq);
        top->left = left;
        top->right = right;

        minHeap->array[0] = top;
        minHeap->size--;

        minHeapify(minHeap, 0);
    }

    return minHeap->array[0];
}

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

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

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

// 进行哈夫曼编码
void HuffmanCodes(char data[], int freq[], int size) {
    struct MinHeapNode* root = buildHuffmanTree(data, freq, size);
    int arr[MAX_TREE_HT], top = 0;
    printCodes(root, arr, top);
}

// 计算压缩率
float compressionRatio(int uncompressed_size, int compressed_size) {
    return (float)(uncompressed_size - compressed_size) / uncompressed_size;
}

// 主函数
int main() {
    char data[] = {'a', 'b', 'c', 'd', 'e', 'f'};
    int freq[] = {5, 9, 12, 13, 16, 45};
    int size = sizeof(data) / sizeof(data[0]);

    HuffmanCodes(data, freq, size);

    // 假设原始文件大小为100字节，压缩后文件大小为60字节
    int uncompressed_size = 100;
    int compressed_size = 60;

    float ratio = compressionRatio(uncompressed_size, compressed_size);

    printf("Compression ratio: %.2f%%\n", ratio * 100);

    return 0;
}

以上代码是一个简单的哈夫曼编码实现，其中 `data` 数组存储字符，`freq` 数组存储对应字符出现的频率，`size` 表示数组的长度。通过 `HuffmanCodes` 函数进行哈夫曼编码并打印出每个字符的编码。最后通过 `compressionRatio` 函数计算压缩率。