Explain test case: [1,null,2,null,3]
I don't really get this case at all!  How does the root's left child (null) have children?\n\nFrom this test case [1, null, 2, null, 3] I gather that the tree l
I don't really get this case at all!  How does the root's left child (null) have children?\n\nFrom this test case [1, null, 2, null, 3] I gather that the tree looks like\n\n            1\n           /  \\\n         #     2\n        /  \\\n      #     3\n\nHow is that possible?
['Tree', 'Binary Tree']