Last updated on October 5th, 2024 at 06:03 pm

Here, We see Convert BST to Greater Tree LeetCode Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc. with different approaches.

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Convert BST to Greater Tree LeetCode Solution

Problem Statement

Given the root of a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus the sum of all keys greater than the original key in BST.

As a reminder, a binary search tree is a tree that satisfies these constraints:

• The left subtree of a node contains only nodes with keys less than the node’s key.
• The right subtree of a node contains only nodes with keys greater than the node’s key.
• Both the left and right subtrees must also be binary search trees.

Example 1:

Input: root = [4,1,6,0,2,5,7,null,null,null,3,null,null,null,8]
Output: [30,36,21,36,35,26,15,null,null,null,33,null,null,null,8]

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

1. Convert BST to Greater Tree LeetCode Solution C++

class Solution {
public:
    TreeNode* convertBST(TreeNode* root) {
        int num = 0;
        solve(root, num);
        return root;        
    }

    void solve(TreeNode *root, int &num)
    {
        if(root == NULL)
            return;
        solve(root->right, num);
        root->val = num + root->val;
        num = root->val;
        solve(root->left, num);
    }
};

2. Convert BST to Greater Tree Solution Java

class Solution {
    int sum = 0;
    public TreeNode convertBST(TreeNode root) {
        if(root==null){
            return root;
        }
        reverseInorder(root);
        return root;
    }
    private void reverseInorder(TreeNode root){
        if(root==null){
            return;
        }
        reverseInorder(root.right);
        root.val = root.val + sum;
        sum = root.val;
        reverseInorder(root.left);
        return;
    }
}

3. Convert BST to Greater Tree Solution JavaScript

var convertBST = function(root) {
    let sum = 0, prev = 0;
    function rec(root){
        if(root){
            rec(root.right);
            sum += root.val;
            root.val += prev;
            prev = sum;
            rec(root.left);
        }
    }
    rec(root);
    return root;
}

4. Convert BST to Greater Tree Solution Python

class Solution(object):
    def convertBST(self, root):
        def dfs(node):
            if node:
                dfs(node.right)
                node.val += dfs.greater_sum
                dfs.greater_sum = node.val
                dfs(node.left)
        dfs.greater_sum = 0
        dfs(root)
        return root