Blind 75 - Maximum Depth of Binary Tree
go to each depth, incrementing a depth counter by 1. return max of it.
go to each depth, incrementing a depth counter by 1. return max of it.
Iterate over both and store minimum one in current; Increment in the list from where minimum came. Once one of the lists is empty, empty the other one.
Check if root is same as subtree or root.left is same or root.right is same;
Make sure the left pointer is always the lowest yet. Keep checking the difference between left and right. And return max.
Have 2 pointers. One at the start other at the end. Skip if `!Character.isLetterOrDigit` and compare with `Character.toLowerCase`
Create a set and put items in one by one while checking if `num` is already there.