Convert Sorted Array to Binary Search Tree | Leetcode

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

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Solution: Take the middle element as the root node. Recurse on left and right sub-arrays and put as children nodes.

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode sortedArrayToBST(int[] nums) {
        return sortedArrayToBST(nums, 0, nums.length - 1);
    }
    
    public TreeNode sortedArrayToBST(int[] nums, int i, int j) {
        if (i > j) return null;
        int mid = i + (j - i) / 2;
        TreeNode node = new TreeNode(nums[mid]);
        node.left = sortedArrayToBST(nums, i, mid - 1);
        node.right = sortedArrayToBST(nums, mid + 1, j);
        return node;
    }
}