在二叉树中插入节点

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def insertNode(root, val):
    if root is None:
        return TreeNode(val)
    
    if val < root.val:
        root.left = insertNode(root.left, val)
    else:
        root.right = insertNode(root.right, val)
    
    return root

# 创建一个二叉树
root = TreeNode(5)
root.left = TreeNode(3)
root.right = TreeNode(7)
root.left.left = TreeNode(2)
root.left.right = TreeNode(4)

# 在二叉树中插入节点
new_val = 6
insertNode(root, new_val)

       5
     /   \
    3     7
   / \   /
  2   4 6