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. Constraints n ≤ 100,000 where n is the number of nodes in root Example 1 Input root = [4, [2, [1, null, null], [3, null, null]], [5, null, null]] Output [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;
post_order(u->right);
acc += u->val;
u->val = acc;
post_order(u->left);
}
Tree* solve(Tree* root) {
acc = 0;
post_order(root);
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) {
dfs(root);
return root;
}
private void dfs(Tree node) {
if (node == null)
return;
dfs(node.right);
int val = node.val;
node.val += sum;
sum += val;
dfs(node.left);
}
}
Solution in Python :
class Solution:
def solve(self, root):
ans = 0
def dfs(root):
nonlocal ans
if not root:
return None
dfs(root.right)
ans += root.val
root.val = ans
dfs(root.left)
dfs(root)
return root
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