108. Convert Sorted Array to Binary Search Tree.cs

// keep in mind, if transform a array to BST, just sort the array first.
public class Solution {
    public TreeNode SortedArrayToBST(int[] nums) {
        if (nums == null || nums.Length == 0) return null;
        return SortedArrayToBST(nums, 0, nums.Length - 1);
    }
    private TreeNode SortedArrayToBST(int[] nums, int left, int right) {
        if (left > right) return null;
        int mid = left + (right - left) / 2;
        TreeNode root = new TreeNode(nums[mid]);
        root.left = SortedArrayToBST(nums, left, mid - 1);
        root.right = SortedArrayToBST(nums, mid + 1, right);
        return root;
    }
}