trees-1

[joshyoon92]

No description provided.

[super30admin]

Validate Binary Search Tree (ValidateBST.java)

Strengths:

• Clean, well-structured recursive solution
• Correct use of min/max bounds approach
• Good variable naming and code organization
• Handles edge cases properly (null checks)

Areas for Improvement:

• Consider adding early termination after flag becomes false to avoid unnecessary recursive calls
• Could add a check at the start of helper to return immediately if flag is already false

Minor suggestions:

• The code could benefit from a comment explaining the min/max bounds logic for future readers

VERDICT: PASS

---

Construct Binary Tree from Preorder and Inorder Traversal (SumRoot.java)

Strengths:

• Clean variable naming (sum, currSum)
• Good base case handling (null check)
• Proper use of helper method with accumulated sum
• Correct leaf node detection (both children null)

Critical Issues:

1. Wrong Problem: This solution solves "Sum Root to Leaf Numbers" (LeetCode 129), not "Construct Binary Tree from Preorder and Inorder Traversal" (LeetCode 105). The problem requires building a tree from two traversal arrays.

2. Missing Tree Construction Logic: The solution needs to:

   • Use the preorder array to identify root values
   • Use the inorder array to determine left/right subtree boundaries
   • Build TreeNode objects recursively

3. Return Type Mismatch: The problem requires returning a TreeNode* (or TreeNode in Java), but this solution returns an int.

To Fix:

• Remove the sum logic entirely
• Implement a recursive approach using preorder index tracking
• Use a HashMap for inorder value-to-index mapping
• Build left and right subtrees recursively based on inorder boundaries

VERDICT: NEEDS_IMPROVEMENT