701. Insert into a Binary Search Tree（在二叉搜索树中插入节点）_insert in binary search tree iterative-优快云博客

本文详细介绍了在二叉搜索树中插入新节点的两种方法：递归和迭代。通过具体的代码实现，展示了如何保持树的搜索特性，同时保证了插入操作的效率。

题目描述

Given the root node of a binary search tree (BST) and a value to be inserted into the tree, insert the value into the BST. Return the root node of the BST after the insertion. It is guaranteed that the new value does not exist in the original BST.

Note that there may exist multiple valid ways for the insertion, as long as the tree remains a BST after insertion. You can return any of them.

在这里插入图片描述

方法思路

Approach1: recursive

class Solution {
    //Runtime: 2 ms, faster than 69.27%
    //Memory Usage: 40.5 MB, less than 6.79%
    public TreeNode insertIntoBST(TreeNode root, int val) {
        if(root == null)
            return new TreeNode(val);
        if(val < root.val)
            root.left = insertIntoBST(root.left, val);
        if(val > root.val)
            root.right = insertIntoBST(root.right, val);
        else;
        
        return root;
    }
}

Approach2: iterative

class Solution{
    //Runtime: 1 ms, faster than 100.00% 
    //Memory Usage: 40.3 MB, less than 38.41% 
    public TreeNode insertIntoBST(TreeNode root, int val) {
        if(root == null) return new TreeNode(val);
        TreeNode cur = root;
        while(true){
            if(val < cur.val){
                if(cur.left != null){
                    cur = cur.left;
                }else{
                    cur.left = new TreeNode(val);
                    break;
                }
                
            }else if(val > cur.val){
                if(cur.right != null){
                    cur = cur.right;
                }else{
                    cur.right = new TreeNode(val);
                    break;
                }
            }else break;
        }
        return root;
    }
}