Enlarge BST - Amazon Top Interview Questions

Problem Statement :

Given a binary search tree root, replace every node's value v by its value plus the sum of all other values in the tree that are greater than v.


n ≤ 100,000 where n is the number of nodes in root

Example 1


root = [4, [2, [1, null, null], [3, null, null]], [5, null, null]]


[9, [14, [15, null, null], [12, null, null]], [5, null, null]]

Solution :


                        Solution in C++ :

int acc;

void post_order(Tree* u) {
    if (!u) return;
    acc += u->val;
    u->val = acc;

Tree* solve(Tree* root) {
    acc = 0;
    return root;

                        Solution in Java :

import java.util.*;

 * public class Tree {
 *   int val;
 *   Tree left;
 *   Tree right;
 * }
class Solution {
    private int sum = 0;
    public Tree solve(Tree root) {
        return root;

    private void dfs(Tree node) {
        if (node == null)
        int val = node.val;
        node.val += sum;
        sum += val;

                        Solution in Python : 
class Solution:
    def solve(self, root):
        ans = 0

        def dfs(root):
            nonlocal ans
            if not root:
                return None
            ans += root.val
            root.val = ans

        return root

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