Insert Node in a Binary Search Tree

Given a binary search tree and a new tree node, insert the node into 
the tree. You should keep the tree still be a valid binary search 
tree. 
Can you do it without recursion?

递归

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */
class Solution {
public:
    /**
     * @param root: The root of the binary search tree.
     * @param node: insert this node into the binary search tree
     * @return: The root of the new binary search tree.
     */
    TreeNode* insertNode(TreeNode* root, TreeNode* node) {
        // write your code here

        if(node==NULL){
            return root;
        }

        if(root==NULL){
            return node;
        }

        if(node->val<root->val){
            root->left=insertNode(root->left,node);
        }else{
            root->right=insertNode(root->right,node);
        }

        return root;
    }
};

• 迭代

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */
class Solution {
public:
    /**
     * @param root: The root of the binary search tree.
     * @param node: insert this node into the binary search tree
     * @return: The root of the new binary search tree.
     */
    TreeNode* insertNode(TreeNode* root, TreeNode* node) {
        // write your code here

        if(node==NULL){
            return root;
        }

        if(root==NULL){
            return node;
        }

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

        return root;
    }
};