用C语言写一个Huffman解压程序

非常感谢您的提问。关于用C语言写一个Huffman解压程序，我可以给您提供一些思路和建议。首先，您需要了解Huffman编码的原理和实现方式，然后根据压缩文件的格式和Huffman编码表，解析出压缩文件中的数据，并进行解码还原。具体的实现过程可以参考相关的算法和数据结构书籍，或者在网上搜索相关的代码实现。希望这些信息能够对您有所帮助。

相关问题

帮我写一个C语言数据解压的程序，分别用LZ77、LZ78、Huffman这三方法

来实现。以下是示例代码：

LZ77解压：

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

#define MAX_BUFFER_SIZE 1024

typedef struct {
int offset;
int length;
char next_char;
} lz77_token;

void lz77_decompress(char* compressed_data, char* decompressed_data) {
int compressed_data_length = strlen(compressed_data);
int decompressed_data_length = 0;
int i = 0;
while (i < compressed_data_length) {
lz77_token token;
memcpy(&token, compressed_data + i, sizeof(lz77_token));
i += sizeof(lz77_token);
if (token.length == 0) {
decompressed_data[decompressed_data_length++] = token.next_char;
} else {
int j;
for (j = 0; j < token.length; j++) {
decompressed_data[decompressed_data_length + j] = decompressed_data[decompressed_data_length - token.offset + j];
}
decompressed_data_length += token.length;
decompressed_data[decompressed_data_length++] = token.next_char;
}
}
decompressed_data[decompressed_data_length] = '\0';
}

LZ78解压：

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

#define MAX_BUFFER_SIZE 1024

typedef struct {
int prefix_index;
char next_char;
} lz78_token;

void lz78_decompress(char* compressed_data, char* decompressed_data) {
int compressed_data_length = strlen(compressed_data);
int decompressed_data_length = 0;
int i = 0;
int dict_size = 0;
char** dictionary = (char**)malloc(MAX_BUFFER_SIZE * sizeof(char*));
memset(dictionary, 0, MAX_BUFFER_SIZE * sizeof(char*));
while (i < compressed_data_length) {
lz78_token token;
memcpy(&token, compressed_data + i, sizeof(lz78_token));
i += sizeof(lz78_token);
if (token.prefix_index == 0) {
decompressed_data[decompressed_data_length++] = token.next_char;
dictionary[++dict_size] = strdup(&decompressed_data[decompressed_data_length - 1]);
} else {
char* new_string = (char*)malloc(MAX_BUFFER_SIZE * sizeof(char));
strcpy(new_string, dictionary[token.prefix_index]);
new_string[strlen(new_string)] = token.next_char;
decompressed_data_length += strlen(new_string);
strcpy(&decompressed_data[decompressed_data_length - strlen(new_string)], new_string);
dictionary[++dict_size] = strdup(new_string);
free(new_string);
}
}
decompressed_data[decompressed_data_length] = '\0';
int j;
for (j = 1; j <= dict_size; j++) {
free(dictionary[j]);
}
free(dictionary);
}

Huffman解压：

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

#define MAX_BUFFER_SIZE 1024

typedef struct {
char character;
char* code;
} huffman_node;

void huffman_decompress(char* compressed_data, char* decompressed_data) {
int compressed_data_length = strlen(compressed_data);
int decompressed_data_length = 0;
int i = 0;
huffman_node* huffman_tree = (huffman_node*)malloc(MAX_BUFFER_SIZE * sizeof(huffman_node));
memset(huffman_tree, 0, MAX_BUFFER_SIZE * sizeof(huffman_node));
while (i < compressed_data_length) {
char character = compressed_data[i++];
char* code = (char*)malloc(MAX_BUFFER_SIZE * sizeof(char));
memset(code, 0, MAX_BUFFER_SIZE * sizeof(char));
int j = 0;
while (compressed_data[i] != '\0') {
code[j++] = compressed_data[i++];
if (huffman_tree[character].code != NULL) {
break;
}
}
huffman_tree[character].character = character;
huffman_tree[character].code = strdup(code);
free(code);
}
char* code = (char*)malloc(MAX_BUFFER_SIZE * sizeof(char));
memset(code, 0, MAX_BUFFER_SIZE * sizeof(char));
i++;
while (i < compressed_data_length) {
code[strlen(code)] = compressed_data[i++];
int j;
for (j = 0; j < 256; j++) {
if (huffman_tree[j].code != NULL && strcmp(huffman_tree[j].code, code) == 0) {
decompressed_data[decompressed_data_length++] = huffman_tree[j].character;
memset(code, 0, MAX_BUFFER_SIZE * sizeof(char));
break;
}
}
}
decompressed_data[decompressed_data_length] = '\0';
int j;
for (j = 0; j < 256; j++) {
if (huffman_tree[j].code != NULL) {
free(huffman_tree[j].code);
}
}
free(huffman_tree);
}

用c语言写一个哈夫曼编码实现文件压缩与解压

哈夫曼编码是一种无损压缩算法，可以将输入的数据流进行压缩，减小数据存储空间，提高数据传输效率。以下是使用 C 语言实现哈夫曼编码的程序，包括文件压缩和解压两个部分。

#### 哈夫曼编码压缩

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

#define MAX_NODES 256

typedef struct {
    unsigned char ch;
    int freq;
} Node;

typedef struct {
    int left_child;
    int right_child;
    int parent;
    int weight;
} HuffmanNode;

void count_frequency(char *filename, int *freq) {
    FILE *fp;
    unsigned char ch;
    if ((fp = fopen(filename, "rb")) == NULL) {
        printf("Cannot open file %s\n", filename);
        return;
    }
    while (fread(&ch, sizeof(unsigned char), 1, fp) == 1) {
        freq[ch]++;
    }
    fclose(fp);
}

int select_min(HuffmanNode *huffman_tree, int n, int *min1, int *min2) {
    int i, cnt = 0;
    for (i = 0; i < n; i++) {
        if (huffman_tree[i].parent == -1) cnt++;
    }
    if (cnt < 2) return 0;
    *min1 = -1, *min2 = -1;
    for (i = 0; i < n; i++) {
        if (huffman_tree[i].parent == -1) {
            if (*min1 == -1 || huffman_tree[i].weight < huffman_tree[*min1].weight) {
                *min2 = *min1;
                *min1 = i;
            } else if (*min2 == -1 || huffman_tree[i].weight < huffman_tree[*min2].weight) {
                *min2 = i;
            }
        }
    }
    return 1;
}

int build_huffman_tree(int *freq, int n, HuffmanNode *huffman_tree) {
    int i, j, min1, min2;
    for (i = 0; i < n; i++) {
        huffman_tree[i].left_child = -1;
        huffman_tree[i].right_child = -1;
        huffman_tree[i].parent = -1;
        huffman_tree[i].weight = freq[i];
    }
    for (i = n; i < 2 * n - 1; i++) {
        if (select_min(huffman_tree, i, &min1, &min2) == 0) break;
        huffman_tree[min1].parent = i;
        huffman_tree[min2].parent = i;
        huffman_tree[i].left_child = min1;
        huffman_tree[i].right_child = min2;
        huffman_tree[i].weight = huffman_tree[min1].weight + huffman_tree[min2].weight;
    }
    return i;
}

int encode(char *filename, char *filename_out, HuffmanNode *huffman_tree, int n) {
    FILE *fp_in, *fp_out;
    unsigned char ch, byte = 0;
    int i, bit_cnt = 0;
    if ((fp_in = fopen(filename, "rb")) == NULL) {
        printf("Cannot open file %s\n", filename);
        return 0;
    }
    if ((fp_out = fopen(filename_out, "wb")) == NULL) {
        printf("Cannot open file %s\n", filename_out);
        return 0;
    }
    while (fread(&ch, sizeof(unsigned char), 1, fp_in) == 1) {
        i = n - 1;
        while (i >= 0) {
            if (huffman_tree[i].left_child != -1 && huffman_tree[huffman_tree[i].left_child].weight <= bit_cnt) {
                byte |= (1 << (7 - bit_cnt));
                i = huffman_tree[i].left_child;
                bit_cnt++;
            } else if (huffman_tree[i].right_child != -1 && huffman_tree[huffman_tree[i].right_child].weight <= bit_cnt) {
                i = huffman_tree[i].right_child;
                bit_cnt++;
            } else {
                break;
            }
            if (bit_cnt == 8) {
                fwrite(&byte, sizeof(unsigned char), 1, fp_out);
                byte = 0;
                bit_cnt = 0;
            }
        }
    }
    if (bit_cnt > 0) {
        fwrite(&byte, sizeof(unsigned char), 1, fp_out);
    }
    fclose(fp_in);
    fclose(fp_out);
    return 1;
}

int decode(char *filename_out, char *filename, HuffmanNode *huffman_tree, int root, int size) {
    FILE *fp_in, *fp_out;
    unsigned char ch, byte = 0;
    int i, bit_cnt = 0, node = root;
    if ((fp_in = fopen(filename_out, "rb")) == NULL) {
        printf("Cannot open file %s\n", filename_out);
        return 0;
    }
    if ((fp_out = fopen(filename, "wb")) == NULL) {
        printf("Cannot open file %s\n", filename);
        return 0;
    }
    while (fread(&ch, sizeof(unsigned char), 1, fp_in) == 1) {
        for (i = 0; i < 8; i++) {
            if (ch & (1 << (7 - i))) {
                node = huffman_tree[node].left_child;
            } else {
                node = huffman_tree[node].right_child;
            }
            if (node < size && node >= 0) {
                fwrite(&huffman_tree[node].weight, sizeof(unsigned char), 1, fp_out);
                node = root;
            }
        }
    }
    fclose(fp_in);
    fclose(fp_out);
    return 1;
}

int main(int argc, char *argv[]) {
    if (argc != 4) {
        printf("Usage: %s [-c/-d] input_file output_file\n", argv[0]);
        return 0;
    }
    if (strcmp(argv[1], "-c") == 0) {
        int freq[MAX_NODES] = {0};
        count_frequency(argv[2], freq);
        HuffmanNode huffman_tree[2 * MAX_NODES - 1];
        int root = build_huffman_tree(freq, MAX_NODES, huffman_tree);
        encode(argv[2], argv[3], huffman_tree, root);
    } else if (strcmp(argv[1], "-d") == 0) {
        int freq[MAX_NODES] = {0};
        count_frequency(argv[3], freq);
        HuffmanNode huffman_tree[2 * MAX_NODES - 1];
        int root = build_huffman_tree(freq, MAX_NODES, huffman_tree);
        decode(argv[2], argv[3], huffman_tree, root, MAX_NODES);
    } else {
        printf("Usage: %s [-c/-d] input_file output_file\n", argv[0]);
        return 0;
    }
    return 0;
}

程序中首先定义了两个结构体 `Node` 和 `HuffmanNode`，分别用于存储字符频率和哈夫曼树节点信息。在 `count_frequency` 函数中，程序读入输入文件中的每个字符，并统计每个字符出现的频率，存储在 `freq` 数组中。接着，在 `build_huffman_tree` 函数中，程序构建哈夫曼树，并返回根节点的位置。在构建哈夫曼树的过程中，程序使用了 `select_min` 函数来选择权值最小的两个节点进行合并。最后，在 `encode` 函数中，程序读入输入文件中的每个字符，并使用哈夫曼树进行编码，并将编码后的结果输出到输出文件中。

#### 哈夫曼编码解压

在解压过程中，程序使用 `decode` 函数来读入输入文件中的每个编码，并使用哈夫曼树进行解码，并将解码后的结果输出到输出文件中。需要注意的是，在解码过程中，程序需要记录当前所在的哈夫曼树节点位置，以便进行下一位的解码。

以上是使用 C 语言实现的哈夫曼编码程序，包括文件压缩和解压两个部分。