二叉树的前序遍历C++实现代码

以下是二叉树的前序遍历C实现代码：

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

typedef struct TreeNode {
    int val; 
    struct TreeNode* left; 
    struct TreeNode* right; 
} TreeNode; 

void preOrder(TreeNode* root) {
    if(root == NULL) 
        return; 
    
    printf("%d ", root -> val); 
    preOrder(root -> left); 
    preOrder(root -> right); 
}

int main() {
    TreeNode* root = (TreeNode*)malloc(sizeof(TreeNode)); 
    root -> val = 1; 
    root -> left = (TreeNode*)malloc(sizeof(TreeNode)); 
    root -> left -> val = 2; 
    root -> left -> left = NULL; 
    root -> left -> right = NULL; 
    root -> right = (TreeNode*)malloc(sizeof(TreeNode)); 
    root -> right -> val = 3; 
    root -> right -> left = (TreeNode*)malloc(sizeof(TreeNode)); 
    root -> right -> left -> val = 4; 
    root -> right -> left -> left = NULL; 
    root -> right -> left -> right = NULL; 
    root -> right -> right = (TreeNode*)malloc(sizeof(TreeNode)); 
    root -> right -> right -> val = 5; 
    root -> right -> right -> left = NULL; 
    root -> right -> right -> right = NULL; 
    
    preOrder(root); 
    
    return 0; 
}

这是一个简单的二叉树数据结构，使用前序遍历方法输出树的节点值。前序遍历的顺序是：先遍历根节点，再遍历左子树，最后遍历右子树。在这个实现中，我们使用了递归来遍历二叉树。