Welcome to Subscribe On Youtube

669. Trim a Binary Search Tree

Description

Given the root of a binary search tree and the lowest and highest boundaries as low and high, trim the tree so that all its elements lies in [low, high]. Trimming the tree should not change the relative structure of the elements that will remain in the tree (i.e., any node's descendant should remain a descendant). It can be proven that there is a unique answer.

Return the root of the trimmed binary search tree. Note that the root may change depending on the given bounds.

 

Example 1:

Input: root = [1,0,2], low = 1, high = 2
Output: [1,null,2]

Example 2:

Input: root = [3,0,4,null,2,null,null,1], low = 1, high = 3
Output: [3,2,null,1]

 

Constraints:

  • The number of nodes in the tree is in the range [1, 104].
  • 0 <= Node.val <= 104
  • The value of each node in the tree is unique.
  • root is guaranteed to be a valid binary search tree.
  • 0 <= low <= high <= 104

Solutions

  • /**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode trimBST(TreeNode root, int low, int high) {
        if (root == null) {
            return root;
        }
        if (root.val > high) {
            return trimBST(root.left, low, high);
        }
        if (root.val < low) {
            return trimBST(root.right, low, high);
        }
        root.left = trimBST(root.left, low, high);
        root.right = trimBST(root.right, low, high);
        return root;
    }
}

  • /**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* trimBST(TreeNode* root, int low, int high) {
        if (!root) return root;
        if (root->val > high) return trimBST(root->left, low, high);
        if (root->val < low) return trimBST(root->right, low, high);
        root->left = trimBST(root->left, low, high);
        root->right = trimBST(root->right, low, high);
        return root;
    }
};

  • # Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def trimBST(
        self, root: Optional[TreeNode], low: int, high: int
    ) -> Optional[TreeNode]:
        def dfs(root):
            if root is None:
                return root
            if root.val > high:
                return dfs(root.left)
            if root.val < low:
                return dfs(root.right)
            root.left = dfs(root.left)
            root.right = dfs(root.right)
            return root

        return dfs(root)


  • /**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func trimBST(root *TreeNode, low int, high int) *TreeNode {
	if root == nil {
		return root
	}
	if root.Val > high {
		return trimBST(root.Left, low, high)
	}
	if root.Val < low {
		return trimBST(root.Right, low, high)
	}
	root.Left = trimBST(root.Left, low, high)
	root.Right = trimBST(root.Right, low, high)
	return root
}

  • /**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */

function trimBST(root: TreeNode | null, low: number, high: number): TreeNode | null {
    const dfs = (root: TreeNode | null) => {
        if (root == null) {
            return root;
        }
        const { val, left, right } = root;
        if (val < low || val > high) {
            return dfs(left) || dfs(right);
        }
        root.left = dfs(left);
        root.right = dfs(right);
        return root;
    };
    return dfs(root);
}


  • /**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @param {number} low
 * @param {number} high
 * @return {TreeNode}
 */
var trimBST = function (root, low, high) {
    function dfs(root) {
        if (!root) {
            return root;
        }
        if (root.val < low) {
            return dfs(root.right);
        }
        if (root.val > high) {
            return dfs(root.left);
        }
        root.left = dfs(root.left);
        root.right = dfs(root.right);
        return root;
    }
    return dfs(root);
};


  • // Definition for a binary tree node.
// #[derive(Debug, PartialEq, Eq)]
// pub struct TreeNode {
//   pub val: i32,
//   pub left: Option<Rc<RefCell<TreeNode>>>,
//   pub right: Option<Rc<RefCell<TreeNode>>>,
// }
//
// impl TreeNode {
//   #[inline]
//   pub fn new(val: i32) -> Self {
//     TreeNode {
//       val,
//       left: None,
//       right: None
//     }
//   }
// }
use std::rc::Rc;
use std::cell::RefCell;
impl Solution {
    pub fn trim_bst(
        mut root: Option<Rc<RefCell<TreeNode>>>,
        low: i32,
        high: i32
    ) -> Option<Rc<RefCell<TreeNode>>> {
        if root.is_none() {
            return root;
        }
        {
            let mut node = root.as_mut().unwrap().borrow_mut();
            if node.val < low {
                return Self::trim_bst(node.right.take(), low, high);
            }
            if node.val > high {
                return Self::trim_bst(node.left.take(), low, high);
            }
            node.left = Self::trim_bst(node.left.take(), low, high);
            node.right = Self::trim_bst(node.right.take(), low, high);
        }
        root
    }
}

All Problems

All Solutions