class Solution {
public TreeNode sortedArrayToBST(int[] nums) {
return dfs(nums,0,nums.length-1);
}
public TreeNode dfs(int[] nums,int left,int right){
if(left>right)return null;
int mid=(left+right)/2;
TreeNode root =new TreeNode(nums[mid]);
root.left=dfs(nums,left,mid-1);
root.right=dfs(nums,mid+1,right);
return root;
}
}