Convert Sorted Array to Binary Search Tree – Solution & Complexity
Solution Walkthrough
Step 1: Recognize the Pattern
The key pattern is: divide and conquer that always roots the subtree at the middle element so both halves stay balanced. Identify the state and invariant before coding.
Step 2: Build the Algorithm
Advance one state transition at a time. Mark or update state before exploring dependent work.
Step 3: Check Edge Cases
Test empty or minimal input, skewed shapes, duplicates where allowed, and impossible outcomes.
Step 4: Solution and Complexity
Time: O(n) — every element becomes exactly one node. Space: O(log n) for the recursion stack on a balanced tree, plus O(n) for the output tree itself.
All 5 languages below run and submit against the remote judge for this problem — Java/Go/Rust use the same real TreeNode structural-type support the judge added for the rest of the linked-list/tree track, and this is the first problem in the bank where TreeNode is the return type rather than only a parameter.
