哈夫曼树文件压缩c语言

以下是使用C语言实现哈夫曼树文件压缩的步骤：

1.读取文件并统计每个字符出现的次数。

FILE *fp;
char ch;
int freq[256] = {0};
fp = fopen("filename.txt", "r");
while((ch = fgetc(fp)) != EOF) {
    freq[ch]++;
}
fclose(fp);

2.构建哈夫曼树。

struct node {
    int freq;
    char data;
    struct node *left, *right;
};
struct node *newNode(int freq, char data) {
    struct node *temp = (struct node*)malloc(sizeof(struct node));
    temp->freq = freq;
    temp->data = data;
    temp->left = temp->right = NULL;
    return temp;
}
struct node *buildHuffmanTree(int freq[]) {
    struct node *left, *right, *top;
    priority_queue<node*, vector<node*>, compare> minHeap;
    for(int i=0; i<256; i++) {
        if(freq[i] != 0) {
            minHeap.push(newNode(freq[i], i));
        }
    }
    while(minHeap.size() != 1) {
        left = minHeap.top();
        minHeap.pop();
        right = minHeap.top();
        minHeap.pop();
        top = newNode(left->freq + right->freq, '$');
        top->left = left;
        top->right = right;
        minHeap.push(top);
    }
    return minHeap.top();
}

3.生成哈夫曼编码。

void generateHuffmanCode(struct node *root, string str, unordered_map<char, string> &huffmanCode) {
    if(!root) {
        return;
    }
    if(root->data != '$') {
        huffmanCode[root->data] = str;
    }
    generateHuffmanCode(root->left, str + "0", huffmanCode);
    generateHuffmanCode(root->right, str + "1", huffmanCode);
}

4.将哈夫曼编码写入文件。

fp = fopen("compressed_file.bin", "wb");
for(int i=0; i<strlen(original_file); i++) {
    fwrite(huffmanCode[original_file[i]].c_str(), sizeof(char), huffmanCode[original_file[i]].size(), fp);
}
fclose(fp);

5.解压缩文件。

fp = fopen("compressed_file.bin", "rb");
while((ch = fgetc(fp)) != EOF) {
    str += ch;
    for(auto i: huffmanCode) {
        if(str == i.second) {
            decompressed_file += i.first;
            str = "";
        }
    }
}
fclose(fp);

6.计算压缩率。

double compressionRatio = (double)compressedFileSize / originalFileSize;

7.比较解压文件是否与原文件内容一致。

if(original_file == decompressed_file) {
    printf("Decompressed file is same as original file.\n");
} else {
    printf("Decompressed file is not same as original file.\n");
}