Create main.c

实验五：哈夫曼编码/main.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+// 定义哈夫曼树节点结构体
+typedef struct {
+    char ch; // 字符
+    int weight; // 权重
+    int parent, lchild, rchild;
+} HTNode, *HuffmanTree;
+
+typedef char **HuffmanCode; // 存放哈夫曼编码
+
+struct Char_frequency {
+    char s; // 字符
+    int f; // 字符出现的频率
+};
+
+HuffmanTree HT; // 全局变量存储赫夫曼树
+HuffmanCode HC; // 全局变量存储赫夫曼编码
+int count1; // 非零字符类型个数
+
+void Select(HuffmanTree HT, int end, int *s1, int *s2);
+void creat_HuffmanTree(HuffmanTree *HT, HuffmanCode *HC, struct Char_frequency *w, int n);
+int calculate_frequency();
+void write_encoded_text(struct Char_frequency* array, HuffmanCode HC, int count1);
+void decode_text(HuffmanTree HT, int count1);
+void compare_files();
+
+int main() {
+      // 计算字符频率
+    if (calculate_frequency() != 0) {
+        // 解码文本
+        decode_text(HT, count1);
+        // 比较文件内容
+        compare_files();
+    }
+    return 0;
+}
+
+void write_encoded_text(struct Char_frequency* array, HuffmanCode HC, int count1) {
+    FILE *inputFile = fopen("D:\\test.txt", "r");
+    FILE *outputFile = fopen("D:\\text2.txt", "w");
+
+    if (inputFile == NULL || outputFile == NULL) {
+        fprintf(stderr, "无法打开文件\n");
+        return;
+    }
+
+    char ch;
+    while ((ch = fgetc(inputFile)) != EOF) {
+        for (int i = 0; i < count1; i++) {
+            if (ch == array[i].s) { // 在哈夫曼编码数组中找到对应的字符
+                fprintf(outputFile, "%s", HC[i + 1]); // 写入对应的哈夫曼编码
+                break;
+            }
+        }
+    }
+
+    fclose(inputFile);
+    fclose(outputFile);
+}
+
+void Select(HuffmanTree HT, int end, int *s1, int *s2) {
+    int min1 = -1, min2 = -1;
+    for (int i = 1; i <= end; i++) {
+        if (HT[i].parent == 0) {
+            if (min1 == -1 || HT[i].weight < HT[min1].weight) {
+                min2 = min1;
+                min1 = i;
+            } else if (min2 == -1 || HT[i].weight < HT[min2].weight) {
+                min2 = i;
+            }
+        }
+    }
+    *s1 = min1;
+    *s2 = min2;
+}
+//创建哈夫曼树
+void creat_HuffmanTree(HuffmanTree *HT, HuffmanCode *HC, struct Char_frequency *w, int n) {
+    if (n <= 1) return;
+    int m = 2 * n - 1;
+    *HT = (HuffmanTree)malloc((m + 1) * sizeof(HTNode)); // 0号单元未用
+    // 初始化哈夫曼树的n个叶子节点的权值和字符
+    for (int i = 1; i <= n; i++) {
+        (*HT)[i].ch = w[i - 1].s; // 字符
+        (*HT)[i].weight = w[i - 1].f; // 字符频率数组下标是从0开始的
+        (*HT)[i].lchild = 0;
+        (*HT)[i].rchild = 0;
+        (*HT)[i].parent = 0;
+    }
+    // 初始化哈夫曼树的n+1到m个分支节点
+    for (int i = n + 1; i <= m; i++) {
+        (*HT)[i].weight = 0;
+        (*HT)[i].lchild = 0;
+        (*HT)[i].rchild = 0;
+        (*HT)[i].parent = 0;
+    }
+    // 构建哈夫曼树
+    for (int i = n + 1; i <= m; i++) {
+        int s1, s2;
+        Select(*HT, i - 1, &s1, &s2); // 选择两个权值最小的节点
+        (*HT)[s1].parent = i;
+        (*HT)[s2].parent = i;
+        (*HT)[i].lchild = s1;
+        (*HT)[i].rchild = s2;
+        (*HT)[i].weight = (*HT)[s1].weight + (*HT)[s2].weight;
+    }
+    // 生成哈夫曼编码,逆向求编码
+    *HC = (HuffmanCode)malloc((n + 1) * sizeof(char *));
+    char *cd = (char *)malloc(n * sizeof(char));
+    cd[n - 1] = '\0';
+    for (int i = 1; i <= n; i++) {
+        int start = n - 1;//编码结束位置
+        for (int c = i, f = (*HT)[c].parent; f != 0; c = f, f = (*HT)[f].parent) {
+            if ((*HT)[f].lchild == c) {
+                cd[--start] = '0';
+            } else {
+                cd[--start] = '1';
+            }
+        }
+        (*HC)[i] = (char *)malloc((n - start) * sizeof(char));
+        strcpy((*HC)[i], &cd[start]);
+         // 打印字符及其对应的哈夫曼编码
+        printf("字符: %c  哈夫曼编码: %s\n", (*HT)[i].ch, (*HC)[i]);
+    }
+
+    free(cd);
+}
+
+int calculate_frequency() {
+    FILE *file;
+    int count = 0;
+    count1 = 0; // 
+    int frequency[127] = {0}; // ASCII码来映射到每个字符的，统计其相应的概率
+    int ch;
+    // 打开文件
+    file = fopen("D:\\test.txt", "r");
+    if (file == NULL) {
+        fprintf(stderr, "无法打开文件\n");
+        return 0;
+    } else {
+        while ((ch = fgetc(file)) != EOF) {
+                 printf("%c",ch);
+            if (ch >= 0 && ch < 127) {
+                frequency[ch]++; // 更新相应字符的频率
+            }
+            count++;
+        }
+    }
+    fclose(file);
+
+    printf("原文字符数：%d\n", count);
+
+    for (int i = 0; i < 127; i++) {
+        printf("%c:%d ", i, frequency[i]);
+        if (frequency[i] != 0)
+            count1++;
+    }
+    printf("\n");
+    printf("非零字符类型：%d\n", count1); // 统计非0字符个数，优化数组方便构建哈夫曼树
+
+    struct Char_frequency *array = (struct Char_frequency *)malloc(sizeof(struct Char_frequency) * count1);
+    if (array == NULL) {
+        fprintf(stderr, "内存分配失败\n");
+        return 0;
+    }
+    int j = 0;
+    for (int i = 0; i < 127; i++) {
+        if (frequency[i] != 0) {
+            array[j].f = frequency[i];
+            array[j].s = i;
+            j++;
+        }
+    }
+    for (int i = 0; i < count1; i++) {
+        printf("%c:%d  ", array[i].s, array[i].f);
+    }
+    printf("\n");
+
+    // 接下来调用哈夫曼树的创建函数生成哈夫曼编码
+    creat_HuffmanTree(&HT, &HC, array, count1);
+
+    // 将原文根据哈夫曼编码写入文件
+    write_encoded_text(array, HC, count1);
+
+    // 释放内存
+    free(array);
+
+    return 0;
+}
+
+void decode_text(HuffmanTree HT, int count1) {
+    FILE *encodedFile = fopen("D:\\text2.txt", "r");
+    FILE *outputFile = fopen("D:\\text3.txt", "w");
+
+    if (encodedFile == NULL || outputFile == NULL) {
+        fprintf(stderr, "无法打开文件\n");
+        return;
+    }
+
+    int root = 2 * count1 - 1; // 赫夫曼树根节点的索引
+    int current = root;
+    char bit;
+
+    while ((bit = fgetc(encodedFile)) != EOF) {
+        if (bit == '0') {
+            current = HT[current].lchild;
+        } else if (bit == '1') {
+            current = HT[current].rchild;
+        }
+
+        if (HT[current].lchild == 0 && HT[current].rchild == 0) { // 叶子节点
+            fputc(HT[current].ch, outputFile); // 输出字符
+            current = root; // 重置为根节点，开始解码下一个字符
+        }
+    }
+
+    fclose(encodedFile);
+    fclose(outputFile);
+}
+void compare_files() {
+    FILE *file1;
+    FILE *file2;
+    int ch1, ch2;
+    // 打开文件
+    file1 = fopen("D:\\test.txt", "r");
+    file2 = fopen("D:\\test3.txt", "r");
+    if (file1 == NULL || file2 == NULL) {
+        fprintf(stderr, "无法打开文件\n");
+        return;
+    } else {
+        while ((ch1 = fgetc(file1)) != EOF && (ch2 = fgetc(file2)) != EOF) {
+            if (ch1 != ch2) {
+                printf("文件存在不同\n");
+                fclose(file1);
+                fclose(file2);
+                return;
+            }
+        }
+
+        if (feof(file1) && feof(file2)) {
+            printf("文件完全一致\n");
+        } else {
+            printf("文件长度不同\n");
+        }
+    }
+
+    // 关闭文件
+    fclose(file1);
+    fclose(file2);
+}