You are correct, lines of code is nothing to do with the difficlty of the problem. I spent close to three weeks writing 12 lines of Python. Two of which consist

You are correct, lines of code is nothing to do with the difficlty of the problem. I spent close to three weeks writing 12 lines of Python. Two of which consisted of print statements. A "clean-up" pass removed three more lines. I consider that to be some of the hardest code I've written in recent memory. If I was asked to invert a binary tree on a whiteboard I would stumble too. Inverting a binary tree, I can walk through the algorithm, or I can bang out the code. And yes, it's three lines of code, but I had to look up what "invert a binary tree" means. Put a pen in my hand and I'd freeze up. It is trivial to solve through either recursion or iteration. I understand how to, but if I was asked to solve it in an interview, I'd definitely question why. I cannot think of a single instance whereby I'd want to legitimately flip a free left to right in its entirety. I can think of dozens of esoteric tree operations that I would need, and have used, but inverting/flipping left-to-right completely is not one of them. I consider the person in that tweet far smarter than me.