Ask an old programmer who's been bitten on the rump by the wrong one.
This is definitely one of those ‘ask a friend’ type things. They can glance at it and give you the answer in seconds.
Next, this is where resources like Stack Overflow shine. Not you asking the question, necessarily, but when you search it'll start with the broadest case and your narrowing it down will teach you the important key concepts to select with.
And that's the problem with a normal database for a problem like this. You need to know how to ask the question, which often leads you right to it on SO or describing it to someone.
Heck, ask your cat, dog or significant other as a last gasp effort. In an interview, ask your interviewer if you're totally lost. It may not win you that specific job, but chances are you'll learn more stuff for the next interview.
Oh, and how us ‘old dudes’ do it? Years of experience with the ‘shape’ of solutions. You develop a feel for where systems break and know to look out for edge cases, literally and figuratively.
Take your search paradigm. If you're searching for lowest weighted path, simplest is root to leaf on a tree, all positive integer lengths. Then you keep adding constraints until your problem looks like an algorithm. That is, you're doing a parallel search between the graph and algorithm characteristics.
And that construct develops over time. I can't give you ‘use x algorithm for y problem’ by name, but I could find it in minutes with a copy of CLRS just using the above model. That is, I know where to start looking and then where to dig once I have the right area.