108. Convert Sorted Array to Binary Search Tree.java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode sortedArrayToBST(int[] nums) {
        
        return createBST(nums, 0 , nums.length-1);


    }

    public TreeNode createBST(int nums[], int l, int r)
    {
        if(l>r)
        {
            return null;
        }
        int mid = l+ (r-l)/2;
        TreeNode root = new TreeNode(nums[mid]);
        root.left = createBST(nums, l, mid-1);
        root.right = createBST(nums, mid+1, r);
        return root;
    }
}