# Leetcode 701. Insert into a Binary Search Tree

2 min readJan 12, 2022

[medium]

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**.

**Example 1:**

**Input:** root = [4,2,7,1,3], val = 5

**Output:** [4,2,7,1,3,5]

**Explanation:** Another accepted tree is:

**Example 2:**

**Input:** root = [40,20,60,10,30,50,70], val = 25

**Output:** [40,20,60,10,30,50,70,null,null,25]

**Example 3:**

**Input:** root = [4,2,7,1,3,null,null,null,null,null,null], val = 5

**Output:** [4,2,7,1,3,5]

**Constraints:**

- The number of nodes in the tree will be in the range
`[0, 104]`

. `-108 <= Node.val <= 108`

- All the values
`Node.val`

are**unique**. `-108 <= val <= 108`

- It’s
**guaranteed**that`val`

does not exist in the original BST.

[Think]

- it’s a BST, if the value large than current node -> right side of tree; smaller than current node -> left side of tree
- create a current node to be a pointer, and return the root at the end of the answer