Recently due to me not having to work on schoolwork, I've been working on leetcode problems. I have to say, the amount of ways one can go about solving a problem are impressive. Plus it's a fun way to learn problem solving. I kind of wish some of my courses hooked me up with some of these types of problems.

For example, I remember having to make a linked list structure. It's nothing difficult, but it would have been fun to manipulate a linked list in the way that leetcode does. In one problem, you have to get the values from two lists' nodes in reverse. Then make it into a number, where you would add those two numbers together, and then reverse insert them into a new list and return that.

In action it looks like this:
list_one  = [1, 0, 9]
list_two = [1]

return [2, 0, 9]

What mind teasers/puzzles have you been doing lately? Or what's one of your favorite leetcode problems (if you've ever done them)?