# 669. Trim a Binary Search Tree

[ **669. Trim a Binary Search Tree**](https://leetcode.com/problems/trim-a-binary-search-tree/description/)

Given a binary search tree and the lowest and highest boundaries as `L` and `R`, trim the tree so that all its elements lies in `[L, R]` (R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed binary search tree.

**Example 1:**<br>

```
Input: 
    1
   / \
  0   2

  L = 1
  R = 2

Output: 
    1
      \
       2
```

**Example 2:**<br>

```
Input: 
    3
   / \
  0   4
   \
    2
   /
  1

  L = 1
  R = 3

Output: 
      3
     / 
   2   
  /
 1
```

***My Solutions:***

```
class Solution {
    public TreeNode trimBST(TreeNode root, int L, int R) {
        if(root==null) return null;
        if(root.val < L) return trimBST(root.right, L, R);
        if(root.val > R) return trimBST(root.left, L, R);
        root.left = trimBST(root.left, L, R);
        root.right = trimBST(root.right, L, R);
        return root;
    }
}
```