帮我写一个实现二叉树前序遍历的C语言程序

以下是实现二叉树前序遍历的C语言程序：

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

// 二叉树节点结构体
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
};

// 前序遍历二叉树
void preorderTraversal(struct TreeNode* root) {
    if (root == NULL) {
        return;
    }
    printf("%d ", root->val);   // 访问当前节点
    preorderTraversal(root->left);   // 遍历左子树
    preorderTraversal(root->right);  // 遍历右子树
}

int main() {
    // 创建二叉树
    struct TreeNode* root = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->val = 1;
    root->left = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->left->val = 2;
    root->left->left = NULL;
    root->left->right = NULL;
    root->right = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->right->val = 3;
    root->right->left = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->right->left->val = 4;
    root->right->left->left = NULL;
    root->right->left->right = NULL;
    root->right->right = (struct TreeNode*)malloc(sizeof(struct TreeNode));
    root->right->right->val = 5;
    root->right->right->left = NULL;
    root->right->right->right = NULL;

    // 前序遍历二叉树
    printf("前序遍历结果：");
    preorderTraversal(root);

    return 0;
}

输出结果为：前序遍历结果：1 2 3 4 5