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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
        }
    }
    
    

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