python 85. Insert Node in a Binary Search Tree

Given binary search tree as follow, after Insert node 6, the tree should be:

  2             2
 / \           / \
1   4   -->   1   4
   /             / \ 
  3             3   6

这是一棵二叉搜索数，左节点小于等于根节点，右节点大于根节点

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

class Solution:
   
    def insertNode(self, root, node):
        # write your code here
        if root is None:
            return node
        if (node.val<=root.val):
            root.left=self.insertNode(root.left,node)
        else:
            root.right=self.insertNode(root.right,node)

        return root

非递归版：

TreeNode* insertNode(TreeNode* root, TreeNode* node) {
        if (NULL == root) {
            return node;
        }

        TreeNode* tempNode = root;
        while (NULL != tempNode) {
            if (node->val <= tempNode->val) {
                if (NULL == tempNode->left) {
                    tempNode->left = node;
                    return root;
                }
                tempNode = tempNode->left;
            } else {
                if (NULL == tempNode->right) {
                    tempNode->right = node;
                    return root;
                }
                tempNode = tempNode->right;
            }
        }