108. Convert Sorted Array to Binary Search Tree.cs

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
public class Solution {
    public TreeNode SortedArrayToBST(int[] nums) {
        
        if(nums.Length ==0) return null; 
        return ConstructTreeFromArray(nums, 0, nums.Length-1);
        
    }
    
    public TreeNode ConstructTreeFromArray(int[] nums, int left, int right)
    {
        if(left>right){
            return null; 
        }
        int midpoint = left + (right-left)/2;
        TreeNode node = new TreeNode(nums[midpoint]);
        
        node.left = ConstructTreeFromArray(nums,left,midpoint-1);
        node.right = ConstructTreeFromArray(nums,midpoint+1,right);
        
        
        return node;
    }
}