Cacher is the code snippet organizer for pro developers

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode upsideDownBinaryTree(TreeNode root) {
        if (root == null || root.left == null && root.right == null) return root;
        TreeNode res = upsideDownBinaryTree(root.left);
        
        root.left.right = root;
        root.left.left = root.right;
        root.right = null;
        root.left = null;
        return res;
        
    }
    
}

/*
[]
[1,2]
[1,2,3,4,5]
[1,2,3,4,5,null,null,6,7]
*/