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public/c/ch4/huffman/halftree.c

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+#include <stdio.h>
+#include <stdlib.h>
+typedef struct Node
+{
+    int weight;
+    struct Node *lChild;
+    struct Node *rChild;
+} Node;
+
+// 比较函数，用于优先队列
+int compare(const void *a, const void *b)
+{
+    return (*(Node **)a)->weight - (*(Node **)b)->weight;
+}
+
+// 创建新的节点
+Node *createNode(int weight)
+{
+    Node *newNode = (Node *)malloc(sizeof(Node));
+    newNode->weight = weight;
+    newNode->lChild = NULL;
+    newNode->rChild = NULL;
+    return newNode;
+}
+// 构建哈夫曼树
+Node *createHuffman(int *weights, int size)
+{
+    Node **nodeArray = (Node **)malloc(size * sizeof(Node *));
+    // 初始化节点数组
+    for (int i = 0; i < size; i++)
+    {
+        nodeArray[i] = createNode(weights[i]);
+        printf("%d,", nodeArray[i]->weight);
+    }
+    qsort(nodeArray, size, sizeof(Node *), compare);
+    for (int i = 0; i < size; i++)
+    {
+        printf("%d-", nodeArray[i]->weight);
+    }
+    // 使用qsort实现优先队列
+    for (int i = size; i > 1; i--)
+    {
+        qsort(nodeArray, i, sizeof(Node *), compare);
+        // 找到最右边两个节点
+        Node *left = nodeArray[i - 1];
+        Node *right = nodeArray[i - 2];
+        // 创建新父节点
+        Node *parent = createNode(left->weight + right->weight);
+        parent->lChild = left;
+        parent->rChild = right;
+        // 将新节点放入数组中
+        nodeArray[i - 2] = parent;
+    }
+
+    Node *root = nodeArray[0];
+    free(nodeArray);
+    return root;
+}
+// 前序遍历输出
+void output(Node *head)
+{
+    if (head == NULL)
+    {
+        return;
+    }
+    printf("%d\n", head->weight);
+    output(head->lChild);
+    output(head->rChild);
+}
+// 释放树的内存
+void freeTree(Node *root)
+{
+    if (root == NULL)
+    {
+        return;
+    }
+    freeTree(root->lChild);
+    freeTree(root->rChild);
+    free(root);
+}
+int main()
+{
+    int weights[] = {2, 18,  9, 3, 7,25};
+    int size = sizeof(weights) / sizeof(weights[0]);
+    Node *huffmanTree = createHuffman(weights, size);
+    printf("前序遍历halftree:\n");
+    output(huffmanTree);
+    // 释放树的内存
+    freeTree(huffmanTree);
+    return 0;
+}