You don't have to memorize 1000 algorithms. Honestly you could have a really good understanding of when and how to use about 10 algorithms and probably do very well on most interviews.
The problem is each company will ask you a different set of algorithms, and you're not sure which they'll ask, so you effectively have to memorize a LOT more than 10 if you want to be prepared for whatever they throw at you (not literally 1000, but maybe 40 or 50, which will take considerable time to prepare for, in addition to all the other preparation or unrelated questions they could end up asking you (architecture, OS, process, design patterns, optimization, advanced language-specific quirks and gotchas, terminology, 3D math and graphics (if games), databases, networking, behavior questions, solving math problems you've never encountered before, questions about your past projects, etc, etc, etc).
When they passed on me after my Google interview, the HR person actually told me "You can try again in 18 months. There are quite a few people who study for it during those 18 months and get it the next time!"
Yeah, I don't want to study for 18 months to get a job at Google, sorry.
The other downside of that is: in 18 months they're going to hassle you for an interview again, whether you want one or not.
I have a friend who was interviewed at Google, rejected, then interviewed again a year later, rejected again, and then a year later a Google recruiter got in touch to see if they'd like another interview. They said it started to feel like a cruel joke.
Oh yeah, recruiters from Google have contacted me three times since then. Actually the most recent recruiter said I could contact her whenever I felt like having another interview.
I might eventually try going through the gauntlet again, but I wasn't quite willing to move to the west coast during that time (new relationship, new home, new puppy, work was going well, I didn't really need more big life changes at that point).
I'm starting to consider a job change but I'm still not sure I want to move to the west coast. I'd probably have to downshift my home quite a bit out there.
You probably won't even get to use all 10 in your 1st two years of work. All the computer science you use in 99% of a typical programming career could be described in a single conference presentation. (Not that one would master all of it that fast, but it would describe what you need to know and know you don't know.)
