first init

c/ch4/huffman/halfcode.c

@@ -0,0 +1,100 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct Node {
+    int weight;
+    struct Node *left, *right;
+} Node;
+
+// 比较函数用于 qsort
+int compare(const void* a, const void* b) {
+    return (*(Node**)a)->weight - (*(Node**)b)->weight;
+}
+
+// 创建新节点
+Node* createNode(int weight) {
+    Node* newNode = (Node*)malloc(sizeof(Node));
+    newNode->weight = weight;
+    newNode->left = newNode->right = NULL;
+    return newNode;
+}
+
+// 构建哈夫曼树
+Node* createHuffmanTree(int* weights, int size) {
+    Node** nodes = malloc(size * sizeof(Node*));
+    for (int i = 0; i < size; i++) {
+        nodes[i] = createNode(weights[i]);
+    }
+    while (size > 1) { 
+        qsort(nodes, size, sizeof(Node*), compare);// 排序节点数组 
+        // 创建父节点
+        Node* parent = createNode(nodes[0]->weight + nodes[1]->weight);
+        parent->left = nodes[0];
+        parent->right = nodes[1];
+        
+        // 替换前两个最小节点
+        nodes[0] = parent;
+        for (int i = 1; i < size - 1; i++) {
+            nodes[i] = nodes[i + 1];
+        }
+        size--;
+    }
+    Node* root = nodes[0];
+    free(nodes);
+    return root;
+}
+
+// 递归生成哈夫曼编码
+void encode(Node* node, char* code, int depth) {
+    if (node->left == NULL && node->right == NULL) {
+        code[depth] = '\0';//终止字符串
+        printf("权重: %d, 编码: %s\n", node->weight, code); 
+        return;
+    }
+    code[depth] = '0';
+    encode(node->left, code, depth + 1);
+    code[depth] = '1';
+    encode(node->right, code, depth + 1);
+}
+
+// 解码函数
+void decode(Node* root, const char* encoded) {
+    Node* current = root;
+    while (*encoded) {
+        if (*encoded == '0') {
+            current = current->left;
+        } else {
+            current = current->right;
+        } 
+        // 到达叶子节点，打印权重并返回根节点
+        if (current->left == NULL && current->right == NULL) {
+            printf("解码权重: %d\n", current->weight);
+            current = root; // 回到根节点
+        }
+        encoded++;// 移动到下一个字符
+    }
+}
+// 释放内存
+void freeTree(Node* node) {
+    if (node) {
+        freeTree(node->left);
+        freeTree(node->right);
+        free(node);
+    }
+}
+
+int main() {
+    int weights[] = {2, 3, 7, 9, 18, 25};
+    int size = sizeof(weights) / sizeof(weights[0]);
+    Node* root = createHuffmanTree(weights, size);
+    char code[100]; // 假设编码长度不会超过100
+    printf("编码:\n");
+    encode(root, code, 0); 
+ 
+    const char* encoded = "0010101111"; 
+    printf("解码-0010101111:\n");
+    decode(root, encoded); 
+
+    freeTree(root);
+    return 0;
+}