Binary Tree in C: Recursive Implementation Guide

In the C language, binary trees can be created using structures and recursive functions. Below is a simple example code:

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

// 定义二叉树的节点结构体
typedef struct Node {
    int data;
    struct Node* left;
    struct Node* right;
} Node;

// 创建新节点
Node* createNode(int data) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = data;
    newNode->left = NULL;
    newNode->right = NULL;
    return newNode;
}

// 递归生成二叉树
Node* createBinaryTree() {
    int data;
    Node* root = NULL;

    printf("输入节点的值（-1表示空节点）：");
    scanf("%d", &data);

    if (data == -1) {
        return NULL;
    }

    root = createNode(data);

    printf("输入%d的左子节点：\n", data);
    root->left = createBinaryTree();

    printf("输入%d的右子节点：\n", data);
    root->right = createBinaryTree();

    return root;
}

// 测试函数
void preorderTraversal(Node* root) {
    if (root != NULL) {
        printf("%d ", root->data);
        preorderTraversal(root->left);
        preorderTraversal(root->right);
    }
}

int main() {
    Node* root = createBinaryTree();

    printf("前序遍历结果：\n");
    preorderTraversal(root);

    return 0;
}

In the code above, we first defined a node structure called Node, then created a function createNode to create new nodes. Next, we used a recursive function createBinaryTree to generate a binary tree where users can input node values, with -1 representing empty nodes. Finally, we output the generated binary tree using the preorderTraversal function.

You can run this code, enter the values of nodes as prompted to generate a binary tree, and output the result of pre-order traversal.