Method dfs

FindElementsInAContaminatedBinaryTree.java:26–32

(TreeNode root, int val)

        
    }
    public void dfs(TreeNode root, int val){
        if(root==null) return;
        root.val = val;
        set.add(val);
        dfs(root.left, 2*val+1);
        dfs(root.right, 2*val+2);
    }
}

/**