【C++代码】二叉树先序递归遍历

void PreOrder(TreeNode* root, vector<int> & temp)
{
    if (root)
    {
        temp.push_back(root->val);
        if (root->left)
        {
            PreOrder_pre(root->left, temp);
        }
        if (root->left)
        {
            PreOrder(root->right, temp);
        }
    }
}
vector<int> PreOrder(TreeNode* root)
{
    vector<int> temp;
    if (!root) return temp;
    PreOrder(root, temp);
    return temp;
}