Is Convert Sorted Array to Binary Search Tree easy or hard?

Convert Sorted Array to Binary Search Tree is categorized as an Easy problem on most coding platforms. The challenge mainly tests understanding of recursion and how the middle element of a sorted array naturally forms the root of a balanced BST.

Convert Sorted Array to Binary Search Tree Python/Java solution

Python and Java implementations typically define a recursive helper function that receives left and right indices. The function calculates the middle index, creates a node, and recursively constructs the left and right subtrees. This pattern produces a balanced BST in O(n) time.

How to solve Convert Sorted Array to Binary Search Tree in O(n)?

Use a recursive divide-and-conquer strategy. Pick the middle element as the root to keep the tree balanced, then recursively build the left subtree from the left half and the right subtree from the right half of the array. Each element is processed once, giving O(n) time complexity.

What is the best approach for Convert Sorted Array to Binary Search Tree?

The recursive middle-element approach is the most efficient method. Select the middle element of the sorted array as the root, recursively build the left subtree from the left half, and the right subtree from the right half. This guarantees a height-balanced BST and runs in O(n) time with O(log n) recursion space.

Is Convert Sorted Array to Binary Search Tree asked at Google/Amazon/Meta?

Convert Sorted Array to Binary Search Tree is a common interview problem used to evaluate understanding of BST properties and divide-and-conquer recursion. Variants of this problem have appeared in interviews at large tech companies including Google, Amazon, and Meta, particularly for roles testing data structure fundamentals.

What data structure is used in Convert Sorted Array to Binary Search Tree?

The problem focuses on constructing a Binary Search Tree from a sorted array. It also relies heavily on recursion and divide-and-conquer techniques to maintain height balance while building the binary tree structure.

What is the time complexity of Convert Sorted Array to Binary Search Tree?

The optimal divide-and-conquer solution runs in O(n) time because each array element becomes a tree node exactly once. The recursion depth corresponds to the height of a balanced BST, which results in O(log n) auxiliary space from the call stack.

Description Solution Video 9:54

108. Convert Sorted Array to Binary Search Tree

Easy75.9% acceptance9 companies

Given an integer array nums where the elements are sorted in ascending order, convert it to a height-balanced binary search tree.

Example 1:

Input: nums = [-10,-3,0,5,9]
Output: [0,-3,9,-10,null,5]
Explanation: [0,-10,5,null,-3,null,9] is also accepted:

Example 2:

Input: nums = [1,3]
Output: [3,1]
Explanation: [1,null,3] and [3,1] are both height-balanced BSTs.

Constraints:

1 <= nums.length <= 10⁴
-10⁴ <= nums[i] <= 10⁴
nums is sorted in a strictly increasing order.

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108. Convert Sorted Array to Binary Search Tree

Asked at 9 companies

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