Cutting Binary Search Tree - Amazon Top Interview Questions

Problem Statement :

Given a binary search tree root, an integer lo, and another an integer hi, remove all nodes that are not between [lo, hi] inclusive.


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

Example 1


root = [2, [1, [0, null, null], null], [4, [3, null, null], null]]
lo = 3
hi = 4


[4, [3, null, null], null]

Example 2


root = [5, [1, null, null], [9, [7, [6, null, null], [8, null, null]], [10, null, null]]]
lo = 7
hi = 10


[9, [7, null, [8, null, null]], [10, null, null]]

Solution :


                        Solution in C++ :

Tree* solve(Tree* root, int lo, int hi) {
    if (!root) return nullptr;
    if (root->val < lo) return solve(root->right, lo, hi);
    if (root->val > hi) return solve(root->left, lo, hi);
    root->left = solve(root->left, lo, hi);
    root->right = solve(root->right, lo, hi);
    return root;

                        Solution in Python : 
class Solution:
    def solve(self, root, lo, hi):

        if root is None:
            return None

        if root.val >= lo and root.val <= hi:
            root.left = self.solve(root.left, lo, hi)
            root.right = self.solve(root.right, lo, hi)
            return root

        elif root.val < lo:
            return self.solve(root.right, lo, hi)

            return self.solve(root.left, lo, hi)

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