701 Insert into a Binary Search Tree

Leetcode

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

Notice 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.

正常插到叶子结点比较容易，其它实现方法可能更复杂且低效

class Solution {
    public TreeNode insertIntoBST(TreeNode root, int val) {
        if(root==null) {
            root=new TreeNode(val);
            return root;
        }
        if(val<root.val){
            root.left= insertIntoBST(root.left,val);
        } else {
            root.right=insertIntoBST(root.right, val);
        }
        return root;
    } 
}