Walkthrough

A new static method construct_bst is added to the BinarySearchTree class that builds a balanced BST from a sorted list using recursive divide-and-conquer. The method designates the middle element as the root and recursively constructs left and right subtrees from the corresponding sublists.

Changes

Sequence Diagram

sequenceDiagram
    participant Caller as Caller
    participant Public as construct_bst()
    participant Helper as _construct_helper()
    participant BST as BinarySearchTree

    Caller->>Public: sorted_list
    rect rgb(200, 220, 240)
        note over Public: Validate input
        Public->>Public: Check if list is empty
    end
    
    Public->>Helper: Call helper(list, 0, len-1)
    rect rgb(220, 240, 220)
        note over Helper: Divide & Conquer
        Helper->>Helper: mid = (left + right) / 2
        Helper->>Helper: Create node at mid
        Helper->>Helper: Recurse left (0 to mid-1)
        Helper->>Helper: Recurse right (mid+1 to end)
    end
    
    Helper->>Public: Return constructed root
    Public->>BST: Wrap root in BinarySearchTree
    BST->>Caller: Return new BST instance

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

• Review the recursive divide-and-conquer logic for correctness (boundary conditions, base cases, middle calculation)
• Verify that empty input is handled correctly (returns None)
• Check edge cases: single-element lists, even/odd-length lists
• Ensure the algorithm produces a balanced tree structure from the sorted input

Possibly related PRs

• feat(datastructures, puzzles): find the closest value in a binary search tree #96: Adds another new public method (find_closest_value_in_bst) to the BinarySearchTree class, indicating a pattern of API expansion for this data structure.

Suggested labels

Datastructures

Poem

🐰 With sorted lists we now can play,
A BST springs forth mid-way,
Divide and conquer, left then right,
Our balanced trees are built just right! 🌳

Pre-merge checks and finishing touches

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