class Solution {

    int[] nums;

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

    public TreeNode sortedArrayToBST(int[] nums) {
        this.nums = nums;
        return dfs(0, nums.length - 1);
    }
}