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Sorted Array to Binary Search Tree

Certification: Basic Level Accuracy: 40% Submissions: 5 Points: 5

Write a Java program to convert a sorted array to a height-balanced binary search tree (BST).

Example 1
    

  • Input: nums = [-10,-3,0,5,9]
    • 

  • Output: [0,-3,9,-10,null,5]
    • 

  • Explanation:

      

    • BST structure:


      BST Tree With Neagative Values
      • 

    

    •
Example 2
    

  • Input: nums = [1,3]
    • 

  • Output: [3,1]
    • 

  • Explanation:

      

    • BST structure:


      BST Tree With Normal Values
      • 

    

    •
Constraints
    

  • 1 ≤ nums.length ≤ 10^4
    • 

  • -10^4 ≤ nums[i] ≤ 10^4
    • 

  • nums is sorted in strictly increasing order
    • 

  • Time Complexity: O(n)
    • 

  • Space Complexity: O(log n)
    •
TreeTech MahindraApple
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Hint
Solution

Solution Hints

    
  
  • Use a recursive approach to build the BST.
    • 
  
  • Choose the middle element of the array as the root.
    • 
  
  • Recursively build left subtree from elements before the middle element.
    • 
  
  • Recursively build right subtree from elements after the middle element.
    • 
  
  • Return the root of the tree.
    •

Steps to solve by this approach:

 Step 1: Check if the input array is null or empty. If so, return null.
 Step 2: Find the middle element of the array - this becomes the root of the BST.
 Step 3: Create a new TreeNode with the middle element's value.
 Step 4: Recursively construct the left subtree using the left half of the array.
 Step 5: Recursively construct the right subtree using the right half of the array.
 Step 6: Return the constructed tree root.
 Step 7: For the recursive case, if left > right, return null (base case).

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