**Leetcode 701. Insert into a Binary Search Tree

Posted 2022-11-25 Z-Pilgrim

https://leetcode.com/problems/insert-into-a-binary-search-tree/description/

想清楚很好写。。

/**
 * Definition for a binary tree node.
 * struct TreeNode 
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) 
 * ;
 */
class Solution 
public:
    
    void dfs(TreeNode* root, TreeNode* pre, int val) 
        if (!root) 
            if (pre && pre->val < val) pre->right = new TreeNode(val);
            else if (pre && pre->val > val) pre->left = new TreeNode(val);
            else root = new TreeNode(val);
            return;
        

        if (root->val > val) 
            dfs(root->left, root, val);
        
        
        if (root->val < val) 
            dfs(root->right, root, val);
        
        
    
    
    TreeNode* insertIntoBST(TreeNode* root, int val) 
        dfs(root, NULL, val);
        return root;
    
;